fleetd #134/#148 point 3: make overlayParity's copy and skip-worktree visible

overlayParity logged everything at debug, so at the default level nobody could
tell which overlay files a spawn actually received (#148 pt 3), and a tracked
file marked --skip-worktree gave no warning that it can no longer be edited
from that worktree (#134).

Report the outcome at info: a per-spawn summary naming the denominator (every
configured candidate), what was copied, and why anything was not — plus a
separate line naming every file marked --skip-worktree, stating plainly that
it cannot be committed from this worktree. No worktree-local marker file: the
worktree must hold exactly the configured overlay set and nothing else, so an
extra file would violate that invariant.

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());
+    }
 }