Phase 1: mechanical echo→chorus rename with back-compat shims

Identity rename, no behavior change (CHORUS-PLAN.md Phase 1):
- Plugin echo-memory → chorus-memory: manifest (v2.0.0-alpha.1), skill dir,
  16 scripts (chorus.py, chorus_config.py, …), EchoError → ChorusError,
  /chorus-* commands, hook paths, docs, scaffold seeds, eval harness,
  build.py. Docs endpoint → chorusapi.mpm.to.
- Env ECHO_* → CHORUS_*; config → ~/.claude/chorus-memory/config.json;
  state dir → ~/.chorus-memory/; marker → _agent/chorus-vault.md.

Back-compat shims (one major version):
- chorus_config aliases legacy ECHO_* env at import; reads a legacy
  echo-memory config.json when no CHORUS config exists (writes never
  land there); doctor/config report the legacy source.
- State dir honors an existing ~/.echo-memory when the new dir is absent
  (offline queue not stranded).
- Marker dual-probe in load/doctor/bootstrap/lint/sweep/migrate: a
  pre-fork _agent/echo-vault.md counts as bootstrapped; bootstrap repair
  won't write a second marker; routing gains agent-marker-legacy (GET).

Verified: 25/25 unit tests, scaffold + routing-sync checks, 4 mock e2e
suites, run_eval metrics unchanged, +6 shim smoke tests green.
Rebuilt chorus-memory.plugin (79 entries).

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

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

@@ -0,0 +1,21 @@
+---
+description: Recall a topic from CHORUS memory — matching notes plus their linked neighbourhood
+argument-hint: "[topic, person, or project]"
+---
+
+Use the **chorus-memory** skill to recall context for:
+
+> $ARGUMENTS
+
+Run the one-call recall — it resolves the term against the entity index, searches, and expands one hop along `## Related` links and `source_notes`, so you get the connected web (linked decisions, people, prior sessions), not an isolated note:
+
+```bash
+CHORUS="${CLAUDE_PLUGIN_ROOT}/skills/chorus-memory/scripts/chorus.py"
+[ -f "$CHORUS" ] || CHORUS=$(ls /sessions/*/mnt/.remote-plugins/*/skills/chorus-memory/scripts/chorus.py 2>/dev/null | head -1)   # CoWork sandbox fallback
+python3 "$CHORUS" recall "$ARGUMENTS"
+# Windows: use `python` or `py -3` if `python3` is not on PATH.
+```
+
+The corpus spans the entity graph **plus session logs and journal notes**, ranked by relevance × freshness × status — each hit shows its `updated:`/`status:`, so prefer fresh/active hits and treat stale ones as history. Add `--json` for structured hits (`path/score/type/updated/status/excerpt`) when you need to act on the results programmatically.
+
+Then answer from the assembled context. If you only need the canonical path for one entity, use `chorus.py resolve "<title>"` instead. Don't narrate the retrieval.