Merge #461: project addendum for the herdr socket carve-out (fleetd #455)

Doc-only, one file, 13 added lines, inside §Project addendum. Verified by me:

- Canonical block byte-identical: 17468 chars on main and on the branch.
- The sync script in CLAUDE.md prints "in sync: True" both before and after.
- The note's own re-measure command works. Run verbatim, it returns exactly the 4 files
  the note names, and no others:
    fleetd/src/test/java/dev/ltms/fleet/herdr/AgentControlContractTest.java
    fleetd/src/test/java/dev/ltms/fleet/herdr/PaneLocatorContractTest.java
    fleetd/src/test/java/dev/ltms/fleet/herdr/WorkspacePlacementContractTest.java
    fleetd/src/test/java/dev/ltms/fleet/herdr/HerdrContractTest.java
  Control that the search reaches the tree: 120 test java files, 63 of them mention herdr.
  That control matters here — a zero-match re-measure command would tell a future session to
  delete a live restriction.
- All four required elements are present: the carve-out, what stays banned (the control plane),
  who it applies to, and the perishable half (dated 2026-09-10, the command, what each outcome
  means, and delete-when-stale).
- Cross-references #458 for the canonical restatement, which is deliberately not in this change.

Pre-send check applied to the note itself: a worker assigned to AgentControlContractTest can now
name one legal action that finishes its task — let the test open the herdr socket in a throwaway
workspace it tears down.

CLAUDE.md

@@ -223,6 +223,19 @@ must obey belongs in the charter, not here.
 - **This repo is the bridge.** The daemon is `fleetd`, its MCP mount is `http://127.0.0.1:8765/mcp`,
   and the code behind the rules above is `mcp/FleetMcp` (tools), `auth/Authz` (the role table),
   `mcp/ConnectionIdentity` (connection→role), and `worker/*Launcher` (`REPLY_CHARTER`).
+- **Herdr socket tests (measured 2026-09-10).** In this repo, herdr is a subject under test. A
+  worker assigned to herdr code, and the lead, may let a test open the herdr socket directly in a
+  throwaway workspace that the test tears down. This only covers
+  `fleetd/src/test/java/dev/ltms/fleet/herdr/AgentControlContractTest.java`,
+  `fleetd/src/test/java/dev/ltms/fleet/herdr/HerdrContractTest.java`,
+  `fleetd/src/test/java/dev/ltms/fleet/herdr/PaneLocatorContractTest.java`, and
+  `fleetd/src/test/java/dev/ltms/fleet/herdr/WorkspacePlacementContractTest.java`. It is not a
+  general licence. Using the herdr CLI or socket to move a real fleet session, pane, or peer stays
+  banned. That is the control plane that invariant 5 protects. Re-measure with
+  `grep -rl 'UnixSocketHerdrClient.connect()' fleetd/src/test/java --include='*.java'`. A non-empty
+  result means tests still open the socket and this note still applies. An empty result means nobody
+  does this any more; delete this section. Canonical invariant 5 restatement is tracked in #458 and
+  is not part of this change.
 - **`fleet_profiles`/`fleet_list` report two separate outage states, and they are not the same
   thing.** *Quarantined* (CB-578) means the backend told us it is out of capacity — a long,
   1800s-default cooldown. *Cooling off* (fleetd #201/#227) means a profile's credential threw two