Phase 3: per-member namespacing — schema 5 (the core group conversion)

One shared vault, per-member namespaces for all churn-prone state:
- _agent/members/<member>/{preferences,current-context,heartbeat,inbox}.md
  + _agent/sessions/<member>/ session logs; shared group-profile.md
  (with auto-rostered ## Members) and inbox/captures/group.md.
- Self-onboarding: load detects a bootstrapped vault lacking THIS
  member's namespace and seeds it (bootstrap.member_bootstrap()).
- load = 8 reads (marker, group profile, my prefs/context/heartbeat,
  shared daily, my inbox, group inbox); heartbeat fallback lists my
  sessions dir; scope show/set is per member.
- Member-tagged shared writes: daily Agent Log lines and entity-update
  dated blocks are '- YYYY-MM-DD [member]: …'; capture --inbox targets
  my inbox; triage lists both inboxes and writes attributed audit lines.
- routing.json: member-anchors / inbox-group / member-segmented session
  routes; single-user anchor paths retired (schema 5). vault_lint runs
  aging-inbox + scope-drift per member. migrate.py 4->5 for alpha vaults.
- Scaffold: member-* seeds ({{MEMBER}}-stamped), group-profile/group-inbox
  seeds, marker schema 5. Docs (SKILL, vault-layout, routing-map,
  bootstrap) synced; manifest -> 2.0.0-alpha.3; rebuilt plugin (81 files).

Verified: all suites green (25/25 unit, scaffold, routing-sync 36 routes,
4 mock e2e, run_eval unchanged) + 19-check two-member smoke: bootstrap ->
self-onboard -> interleaved tagged daily log -> cross-member update
attribution -> independent scopes -> mine/group triage -> lint clean.

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

README.md

@@ -1,10 +1,10 @@
-# chorus-memory — v2.0.0-alpha.2
+# chorus-memory — v2.0.0-alpha.3
 
 > **CHORUS is a group-based fork of [ECHO](https://git.alwisp.com/jason/echo)** — one shared
 > Obsidian vault serving a group of members instead of a single operator. The conversion
 > plan and settled design decisions live in [CHORUS-PLAN.md](CHORUS-PLAN.md). The pre-fork
-> ECHO v1.5.1 state is preserved at the `echo-fork-point` tag. **Phase 1 (mechanical
-> rename) is done**; the body of this README below the fold still describes the
+> ECHO v1.5.1 state is preserved at the `echo-fork-point` tag. **Phases 1–3 (through per-member
+> namespacing) are done**; the body of this README below the fold still describes the
 > inherited single-operator behavior and is rewritten in Phase 5.
 > Deployment endpoint: `https://chorusapi.mpm.to`. CHORUS is a **clean break** from
 > ECHO — fresh vaults on fresh machines; it carries no ECHO back-compat and never