fleetd #134 + #148 point 3: make the parity overlay say what it did

Both defects lived in one method. overlayParity logged every step at debug, so at the
default level the copy was silent and nobody could tell which overlay files a member
actually got. It also marked a copied tracked file --skip-worktree and said nothing, so a
worker editing that file later found git ignoring the change with no error anywhere.

The summary now reports the denominator, not a bare count: 'copied 1 of 2 candidates:
.env (.envrc absent)'. A bare 'copied 1' is the same under-reporting shape as #113.
Neutralised files are named with the consequence in the message itself.

No marker file is written into the worktree: acceptance criterion 1 requires the worktree
to hold exactly the configured overlay set, so a marker would violate the fix it documents.

The copy and mark logic is unchanged — only logging is new.

Verified by the lead: baseline 1168 tests, 0 failures. Reverting either log.info to
log.debug goes red (2 reds and 1 red, 0 compile errors each), which is the regression that
matters since the whole fix is the log level.

fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java

@@ -486,25 +486,46 @@ public final class GitWorktrees implements Worktrees {
         }
         Path srcRoot = Path.of(repoRoot).toAbsolutePath().normalize();
         Path dstRoot = Path.of(worktreePath).toAbsolutePath().normalize();
+        List<String> copied = new ArrayList<>();
+        List<String> skipped = new ArrayList<>();
+        List<String> neutralized = new ArrayList<>();
         for (String rel : overlay) {
             Path src = srcRoot.resolve(rel).normalize();
             if (!Files.exists(src)) {
-                log.debug("parity overlay source missing — skipping {}", rel);
+                skipped.add(rel + " absent");
                 continue;
             }
             Path dst = dstRoot.resolve(rel).normalize();
             try {
                 Files.createDirectories(dst.getParent());
                 Files.copy(src, dst, StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES);
-                log.debug("copied parity overlay {}", rel);
+                copied.add(rel);
             } catch (IOException e) {
                 throw new WorktreeException("cannot copy overlay " + rel + ": " + e.getMessage(), e);
             }
             if (isTracked(dstRoot, rel)) {
                 exec("git", "-C", worktreePath, "update-index", "--skip-worktree", rel);
-                log.debug("marked overlay --skip-worktree {}", rel);
+                neutralized.add(rel);
             }
         }
+        // CB-148 point 3: a bare count ("copied 1") hides which candidates were even considered — the
+        // same shape of under-reporting this repo has been bitten by before. Name the denominator
+        // (every configured candidate), what was actually copied, and — for anything not copied —
+        // why, so a spawn's overlay outcome is legible from the log alone, no filesystem dig required.
+        String detail = copied.isEmpty() ? String.join(", ", skipped)
+                : skipped.isEmpty() ? String.join(", ", copied)
+                : String.join(", ", copied) + " (" + String.join(", ", skipped) + ")";
+        log.info("parity overlay: copied {} of {} candidates: {}", copied.size(), overlay.size(), detail);
+        // CB-134: a neutralized tracked file is otherwise a silent trap — a worker edits it, git
+        // ignores the change with no error, and nothing anywhere said the file could not be
+        // committed from this worktree. Name every file marked --skip-worktree here, with the
+        // consequence stated in the message itself, rather than adding a worktree-local marker
+        // file: acceptance criterion 1 requires the worktree hold exactly the configured overlay
+        // set and nothing else, so an extra marker would itself violate the fix.
+        if (!neutralized.isEmpty()) {
+            log.info("parity overlay marked --skip-worktree (cannot be committed from this worktree): {}",
+                    String.join(", ", neutralized));
+        }
     }
 
     @Override

fleetd/src/test/java/dev/ltms/fleet/session/GitWorktreesTest.java

@@ -1177,4 +1177,112 @@ class GitWorktreesTest {
                     + "the refusal must happen before `git worktree add` ever runs");
         }
     }
+
+    // ---- fleetd #134 / #148 point 3: overlayParity must report what it did, and marking a tracked
+    // file --skip-worktree must say the file can no longer be committed from this worktree. Drives
+    // overlayParity directly against a real worktree (git worktree add, no GitWorktrees#add) so these
+    // tests are independent of origin/credential-helper provisioning, which is not under test here. ----
+
+    /** A bare worktree, sibling to {@code repo}, created with plain git — the target overlayParity
+     *  copies into. Deliberately not {@link GitWorktrees#add}: that method does unrelated
+     *  provisioning (origin rewrite, .mcp.json neutralization, credential helper) that would only
+     *  add noise to the log assertions below. */
+    private static Path bareWorktree(Path repo, Path wtDir, String branch) throws Exception {
+        git(repo, "worktree", "add", "-q", wtDir.toString(), "-b", branch, "HEAD");
+        return wtDir;
+    }
+
+    /** Acceptance criterion 1: only the configured candidates land in the worktree — nothing else
+     *  from the source tree leaks in alongside them. */
+    @Test
+    void overlayParityCopiesExactlyTheConfiguredFilesAndNothingElse(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        Files.writeString(repo.resolve(".env"), "A=1\n");
+        Files.writeString(repo.resolve(".envrc"), "export A=1\n");
+        Files.writeString(repo.resolve("not-overlaid.txt"), "must not be copied\n");
+        Path wt = bareWorktree(repo, tmp.resolve("wt"), "cb134-exact");
+
+        new GitWorktrees(tmp.resolve("wts").toString())
+                .overlayParity(repo.toString(), wt.toString(), List.of(".env", ".envrc"));
+
+        assertEquals("A=1\n", Files.readString(wt.resolve(".env")));
+        assertEquals("export A=1\n", Files.readString(wt.resolve(".envrc")));
+        assertFalse(Files.exists(wt.resolve("not-overlaid.txt")),
+                "overlayParity must copy only the configured candidates, not the whole source tree");
+    }
+
+    /** Criterion 2: both candidates present — the summary line names both and the denominator. */
+    @Test
+    void overlayParityLogsBothCopiedWhenBothCandidatesArePresent(@TempDir Path tmp) throws Exception {
+        reportingLogger.setLevel(Level.INFO);
+        Path repo = initRepo(tmp.resolve("repo"));
+        Files.writeString(repo.resolve(".env"), "A=1\n");
+        Files.writeString(repo.resolve(".envrc"), "export A=1\n");
+        Path wt = bareWorktree(repo, tmp.resolve("wt"), "cb134-both");
+
+        new GitWorktrees(tmp.resolve("wts").toString())
+                .overlayParity(repo.toString(), wt.toString(), List.of(".env", ".envrc"));
+
+        assertTrue(capturedMessages().contains("parity overlay: copied 2 of 2 candidates: .env, .envrc"),
+                "expected the both-copied summary line, got:\n" + capturedMessages());
+    }
+
+    /** Criterion 2: one candidate present, one absent — the summary must name the copied file, the
+     *  denominator, and why the other candidate was not copied. */
+    @Test
+    void overlayParityLogsOneCopiedOneAbsent(@TempDir Path tmp) throws Exception {
+        reportingLogger.setLevel(Level.INFO);
+        Path repo = initRepo(tmp.resolve("repo"));
+        Files.writeString(repo.resolve(".env"), "A=1\n");
+        // .envrc deliberately not created — the absent candidate.
+        Path wt = bareWorktree(repo, tmp.resolve("wt"), "cb134-partial");
+
+        new GitWorktrees(tmp.resolve("wts").toString())
+                .overlayParity(repo.toString(), wt.toString(), List.of(".env", ".envrc"));
+
+        assertTrue(Files.exists(wt.resolve(".env")));
+        assertFalse(Files.exists(wt.resolve(".envrc")));
+        assertTrue(capturedMessages().contains("parity overlay: copied 1 of 2 candidates: .env (.envrc absent)"),
+                "expected the copied/absent summary line, got:\n" + capturedMessages());
+    }
+
+    /** Criterion 3: a tracked candidate is marked --skip-worktree, and that must be named in the log
+     *  with the consequence spelled out — a worker editing it afterward finds git ignoring the
+     *  change, silently, unless this line told it so beforehand. */
+    @Test
+    void overlayParityLogsSkipWorktreeConsequenceForATrackedFile(@TempDir Path tmp) throws Exception {
+        reportingLogger.setLevel(Level.INFO);
+        Path repo = initRepo(tmp.resolve("repo"));
+        Files.writeString(repo.resolve(".env"), "A=1\n");
+        git(repo, "add", ".env");
+        git(repo, "commit", "-q", "-m", "track env");
+        Path wt = bareWorktree(repo, tmp.resolve("wt"), "cb134-tracked");
+        // Change the source after the worktree checkout, so the overlay copy actually overwrites it.
+        Files.writeString(repo.resolve(".env"), "A=2\n");
+
+        new GitWorktrees(tmp.resolve("wts").toString())
+                .overlayParity(repo.toString(), wt.toString(), List.of(".env"));
+
+        assertEquals("A=2\n", Files.readString(wt.resolve(".env")));
+        assertEquals("", status(wt, ".env"),
+                "the skip-worktree'd file must not show as modified even though its content changed");
+        assertTrue(capturedMessages().contains(
+                        "parity overlay marked --skip-worktree (cannot be committed from this worktree): .env"),
+                "expected the skip-worktree consequence line, got:\n" + capturedMessages());
+    }
+
+    /** Criterion 5: null and empty overlay lists return quietly — no exception, no log noise. */
+    @Test
+    void overlayParityWithNoCandidatesLogsNothing(@TempDir Path tmp) throws Exception {
+        reportingLogger.setLevel(Level.INFO);
+        Path repo = initRepo(tmp.resolve("repo"));
+        Path wt = bareWorktree(repo, tmp.resolve("wt"), "cb134-empty");
+        GitWorktrees worktrees = new GitWorktrees(tmp.resolve("wts").toString());
+
+        worktrees.overlayParity(repo.toString(), wt.toString(), null);
+        worktrees.overlayParity(repo.toString(), wt.toString(), List.of());
+
+        assertTrue(reportingAppender.list.isEmpty(),
+                "a null/empty overlay must log nothing, got:\n" + capturedMessages());
+    }
 }