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-load.md

@@ -14,6 +14,6 @@ python3 "$CHORUS" load
 
 `load` prints all eight sections (and self-onboards your member namespace on a first visit) (404s on today's note / inbox are shown as absent, not errors) and flags an un-bootstrapped vault. Follow up with `chorus.py scope show` if you need the sessions-since-switch count, and a project search if a specific project is in play.
 
-**If `load` prints `NOT CONFIGURED` (exit 78)**, this machine has no usable key file yet. Don't proceed with memory — follow **First run** in `SKILL.md`: tell the operator CHORUS isn't configured, ask for their chorus-memory config file (group/member/endpoint/key), install it with `chorus.py config import <path>` (or `config set`), then re-run `load`.
+**If `load` prints `NOT CONFIGURED` (exit 78)**, this machine has no usable key file yet. Don't proceed with memory — follow **First run** in `SKILL.md`: tell the member CHORUS isn't configured, ask for their chorus-memory config file (group/member/endpoint/key), install it with `chorus.py config import <path>` (or `config set`), then re-run `load`.
 
 Do not narrate the reads. End with a one-line orientation: who/what/where the active scope is, and any reconcile prompt.