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>

chorus-memory.plugin.src/commands/chorus-doctor.md

@@ -16,5 +16,5 @@ bootstrapped (+ `schema_version`), and the **config source** for owner/endpoint/
 (per-field: env override `CHORUS_OWNER`/`CHORUS_BASE`/`CHORUS_KEY`, then the machine-local
 `~/.claude/chorus-memory/config.json` — or `baked-in (plugin)` on a per-user baked build,
 which is authoritative and reported as such). Exits non-zero if anything is red — if the config is
-missing (or still the placeholder template), ask the operator for their chorus-memory config file and install it with `chorus.py config import <path>` (or `config set --owner … --endpoint … --key …`). For the full vault-invariant lint, run
+missing (or still the placeholder template), ask the member for their chorus-memory config file and install it with `chorus.py config import <path>` (or `config set --owner … --endpoint … --key …`). For the full vault-invariant lint, run
 `/chorus-health`.