Phase 5: group-voice docs, onboarding runbook, CHORUS icon — v2.0.0-rc.1

The final phase of CHORUS-PLAN.md. Code- and doc-complete for group use;
rc pends live deployment at chorusapi.mpm.to.

- Repo README rewritten for CHORUS: group model (schema 5), concurrency
  posture, configuration, baked-build onboarding, layout, testing, 2.0
  version history (ECHO history referenced at the fork tag).
- Operator→member voice sweep across SKILL.md (incl. the trigger
  description, now group-aware), all references, 8 command docs, plugin
  README; member preferences / semantic layer / triage guidance describe
  the group model.
- docs/ONBOARDING.md: member runbook — vault stand-up, per-member config,
  bake, deliver, self-onboarding first load, norms, offboarding.
- docs/USAGE.md rewritten as the member usage guide.
- New icon: chorus-icon.svg + 1024/512/64 PNGs (three voices, one center).
- Removed ECHO-era assets (icons, spec PDF, perf briefs); ECHO planning
  docs retired to docs/history/. All preserved at echo-fork-point.
- eval/README documents test_multimember.py. Manifest -> 2.0.0-rc.1;
  rebuilt chorus-memory.plugin.

Verified: routing-sync, 25/25 unit, scaffold, 5 mock e2e suites,
run_eval metrics green.

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

eval/README.md

@@ -29,6 +29,7 @@ python3 test_features.py         # end-to-end features vs the mock (capture/reca
 python3 test_reflect.py          # reflection pipeline
 python3 test_offline_queue.py    # H2 outage queue + read cache
 python3 test_patch_semantics.py  # real PATCH semantics vs mock_olrapi_hifi.py (incl. fm create-or-replace)
+python3 test_multimember.py      # 26-check two-member group lifecycle (bootstrap → self-onboard → attributed writes)
 # plus, in the plugin tree: scripts/test_chorus_client.py (offline unit + routing-sync guard)
 ```