fleetd #669: fix fleetd.example.yaml's false scan-exclusion claims; cover the shipped shape

fleetd.example.yaml claimed member spaces are excluded from the lead-tab scan and that
a lead's workspace default is "leads" and must not match a member workspace. Both are
false: production always passes an empty excludedWorkspaceLabels set (CB-558), and a
lead's workspace defaults to the same shared "fleet" space the members use. Rewrite
both paragraphs to name the defenses that actually exist: the startup tabPrefix refusal
and CallerResolver's roster-first precedence.

Add the test nobody wrote: a lead is still discovered when its workspace label equals
the member workspace, with an empty exclusion set. Correct
aTabInAWorkerSpaceIsNeverALeadEvenWhenItsLabelMatches's javadoc, which overclaimed that
the excludedWorkspaceLabels parameter is the live production guard. Drop the stale line
number from FleetdAssemblyLeadTabScannerExclusionTest's assertion message and javadoc.

fleetd/fleetd.example.yaml

@@ -62,11 +62,12 @@ bind:
 #
 # Leads are configured under `fleet.leaders:` — see THE FLEET further down.
 #
-# Two things stop the tab-name convention from becoming a way to claim leadership: the configured
-# member spaces are excluded from the scan, so nothing fleetd places can land in a matching tab;
-# and startup REFUSES a `tabPrefix` that the fleet tabLabel template, or any per-profile `tabLabel`
-# override, also matches — so the two namespaces cannot overlap by accident. The label is a NAME,
-# never a capability: what a pane may do is decided by the role the daemon resolves for it.
+# Two things stop the tab-name convention from becoming a way to claim leadership: startup REFUSES
+# a `tabPrefix` that the fleet tabLabel template, or any per-profile `tabLabel` override, also
+# matches, so the two namespaces cannot overlap by accident; and the CallerResolver asks the live
+# spawned-member roster BEFORE any tab map, so a live member is never mistaken for a lead no matter
+# what its tab says. The label is a NAME, never a capability: what a pane may do is decided by the
+# role the daemon resolves for it.
 
 # CB-551: IDLE-LEAD HEARTBEAT — nudge the single lead back to work when it has been continuously
 # idle (no open fleet_send driving it) past the quiet period. The fleet is one lead + architects +
@@ -659,9 +660,10 @@ fleet:
   #     tabPrefix: "lead:"           # only used to guard against a worker tabLabel colliding with
   #                                  # this convention at startup; plays no part in matching a lead
   #     scanIntervalSeconds: 10      # rescan cadence, and the worst case before a new tab is seen
-  #     workspace: leads             # where a launched lead's tab is created (default "leads").
-  #                                  # MUST NOT be a member workspace — those are excluded from the
-  #                                  # scan, so a lead placed in one is never found again.
+  #     workspace: leads             # where a launched lead's tab is created (default "fleet",
+  #                                  # the same shared space the members use). Sharing that space
+  #                                  # with members is the normal shipped shape: the scanner tells
+  #                                  # a lead from a member by the exact tab label, not by workspace.
   #     cwd: /path/to/repo           # the launched lead's working directory (default: fleetd's own)
   #     kind: claude                 # descriptive; reported by fleet_whoami
   #   gpt-sol-5.6:

fleetd/src/test/java/dev/ltms/fleet/FleetdAssemblyLeadTabScannerExclusionTest.java

@@ -31,8 +31,7 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
  * fleetd #670 — pins the {@code excludedWorkspaceLabels} argument {@link FleetdAssembly}'s
- * production boot path passes to {@link LeadTabScanner} at {@code FleetdAssembly.java:265}
- * ({@code Set.of()}).
+ * production boot path passes to {@link LeadTabScanner} ({@code Set.of()}).
  *
  * <p>{@code LeadTabScannerTest} already covers this constructor parameter, but it builds its own
  * {@link LeadTabScanner} with its own set, so it tests the seam and proves nothing about the
@@ -191,7 +190,7 @@ class FleetdAssemblyLeadTabScannerExclusionTest {
             Set<?> excluded = (Set<?>) excludedField.get(leads);
 
             assertTrue(excluded.isEmpty(),
-                    "FleetdAssembly.java:265 must pass an empty excludedWorkspaceLabels to "
+                    "FleetdAssembly must pass an empty excludedWorkspaceLabels to "
                             + "LeadTabScanner — scanning member tabs would demote the lead to a worker");
         } finally {
             assertNotNull(ports.shutdownHook, "control: assembly must capture its shutdown hook");

fleetd/src/test/java/dev/ltms/fleet/herdr/LeadTabScannerTest.java

@@ -205,9 +205,12 @@ class LeadTabScannerTest {
     }
 
     /**
-     * The guard that matters: fleetd labels its own worker tabs, so if a worker space were scanned
-     * a naming accident would promote the fleet. The exclusion is by workspace, not by hoping the
-     * worker template never collides.
+     * Covers the {@code excludedWorkspaceLabels} parameter: a tab in an excluded workspace is never
+     * matched, whatever its label. Production always constructs this class with an empty set (CB-558,
+     * {@code FleetdAssembly}), so this parameter plays no part in the live guard against a worker
+     * tab being mistaken for a lead — that guard is {@code CallerResolver} asking the live
+     * spawned-member roster before any tab map. This test exists because the parameter still exists
+     * and is worth covering on its own terms.
      */
     @Test
     void aTabInAWorkerSpaceIsNeverALeadEvenWhenItsLabelMatches() {
@@ -219,6 +222,29 @@ class LeadTabScannerTest {
         assertFalse(scanner(herdr, tabToName, new AtomicLong()).get().containsKey("term_impostor"));
     }
 
+    /**
+     * The shipped shape (CB-558, {@code FleetdAssembly}): production always constructs this class
+     * with an empty {@code excludedWorkspaceLabels}, and a lead's {@code workspace:} default is the
+     * same shared {@code "fleet"} space the members use. A lead tab is still found when it sits in
+     * the exact same workspace as a member-labelled tab — the scanner tells them apart by the exact
+     * tab label, not by which workspace either one is in.
+     */
+    @Test
+    void aLeadIsDiscoveredWhenItsWorkspaceIsTheSameAsTheMemberWorkspace() {
+        TopologyHerdr herdr = new TopologyHerdr()
+                .workspace("w1", "fleet")
+                .tab("w1:t1", "w1", "lead: opus-5.0")
+                .tab("w1:t2", "w1", "worker: gx10 #1")
+                .pane("w1:p1", "w1:t1", "term_opus")
+                .pane("w1:p2", "w1:t2", "term_worker");
+        LeadTabScanner s = new LeadTabScanner(herdr, Map.of("lead: opus-5.0", "opus-5.0"),
+                Set.of(), TTL, new AtomicLong()::get);
+
+        assertEquals("opus-5.0", s.get().get("term_opus"),
+                "a lead sharing the members' workspace is still discovered — the label, not the "
+                        + "workspace, is what matches it");
+    }
+
     @Test
     void aLabelWithNoConfiguredEntryIsIgnored() {
         TopologyHerdr herdr = new TopologyHerdr().workspace("w1", "main")