Phase 4: shared-write hardening + group lenses

- vault_lock gains bounded retry/backoff (CHORUS_LOCK_RETRIES=4,
  CHORUS_LOCK_BACKOFF=0.5s); atomic_index_update and recall-index upkeep
  retry acquisition — unlocked fallback only after exhausted retries,
  loudly, so an already-written note is never stranded unindexed.
- Duplicate-gate candidates carry the existing note's author; STOP
  message says whose entity the capture collided with.
- recall --author <member> filters hits + linked context to one member's
  notes; recall briefs and --json surface the author: stamp.
- load --all-members appends a group-wide view (every member's scope +
  last-session heartbeat); roster parsing accepts folders as
  trailing-slash file entries (the REST API's actual shape).
- operating-contract.md concurrency section rewritten for N members.
- Two-member e2e suite committed as eval/test_multimember.py (26 checks
  incl. all four Phase-4 behaviors).
- Manifest -> 2.0.0-alpha.4; rebuilt chorus-memory.plugin.

Verified: 25/25 unit, scaffold, routing-sync, 5 mock e2e suites (incl.
new multimember), run_eval metrics unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

chorus-memory.plugin.src/skills/chorus-memory/SKILL.md

@@ -64,7 +64,7 @@ All paths below are under `${CLAUDE_PLUGIN_ROOT}/skills/chorus-memory/`. **Invok
 ```bash
 CHORUS="${CLAUDE_PLUGIN_ROOT}/skills/chorus-memory/scripts/chorus.py"   # call as: python3 "$CHORUS" <cmd> ...
 [ -f "$CHORUS" ] || CHORUS=$(ls /sessions/*/mnt/.remote-plugins/*/skills/chorus-memory/scripts/chorus.py 2>/dev/null | head -1)   # CoWork sandbox fallback
-python3 "$CHORUS" load                          # cold-start: the 8 orientation reads in one call
+python3 "$CHORUS" load [--all-members]         # cold-start: the 8 orientation reads (+ optional every-member scope/last-session view)
 python3 "$CHORUS" get   <path>                  # 404 -> exit 44
 python3 "$CHORUS" ls    <dir>   ;  python3 "$CHORUS" map <path>    # listing / document-map
 python3 "$CHORUS" search <terms...>
@@ -166,7 +166,7 @@ Keep the reconcile to a single short line to the operator (e.g. "3 inbox capture
 **If a specific topic/project/person is in play**, pull its connected context in one call:
 
 ```bash
-python3 "$CHORUS" recall "<topic or title>"   # the matching notes AND their one-hop neighbourhood
+python3 "$CHORUS" recall "<topic or title>" [--author <member>]   # matching notes + one-hop neighbourhood (optionally one member's only)
 ```
 
 `recall` resolves the term against the entity index, searches, and expands one hop along `## Related` links and `source_notes` — so you get the project note *plus* its linked decisions, people, and prior sessions, not an isolated file. (If you only need the canonical path, `resolve "<title>"` is the O(1) lookup.)