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>

README.md

@@ -1,10 +1,20 @@
-# echo-memory — v1.5.1
+# chorus-memory — v2.0.0-alpha.1
 
-Persistent memory for Claude / CoWork sessions via the **ECHO** Obsidian vault, driven over the [Obsidian Local REST API](https://github.com/coddingtonbear/obsidian-local-rest-api). The skill makes direct REST calls through a bundled validated client (`scripts/echo.py`). The whole toolchain is **pure Python** (stdlib only), so it runs identically on Windows, macOS, and Linux — no bash, no platform-specific `date`.
+> **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, back-compat shims) is 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`. Legacy `ECHO_*` env vars, an existing
+> `~/.claude/echo-memory/config.json`, and a vault's old `_agent/echo-vault.md` marker
+> all keep working for one major version.
 
-Architected by **Jason Stedwell**. As of **v1.3** the plugin is **user-agnostic**: it ships no owner, endpoint, or API key — each machine supplies them through a local config file (see [Configuration](#configuration)), so the same plugin works for any owner and any vault.
+Persistent memory for Claude / CoWork sessions via the **CHORUS** Obsidian vault, driven over the [Obsidian Local REST API](https://github.com/coddingtonbear/obsidian-local-rest-api). The skill makes direct REST calls through a bundled validated client (`scripts/chorus.py`). The whole toolchain is **pure Python** (stdlib only), so it runs identically on Windows, macOS, and Linux — no bash, no platform-specific `date`.
 
-This repository (`jason/echo-v.05`) holds the plugin **source** (tracked tree at `echo-memory.plugin.src/`), the built `echo-memory.plugin` package artifact (rebuilt on each version bump), and a credential-free A/B `eval/` harness.
+Architected by **Jason Stedwell**. The plugin is **user-agnostic**: it ships no owner, endpoint, or API key — each machine supplies them through a local config file (see [Configuration](#configuration)), so the same plugin works for any group and any vault.
+
+This repository (`jason/chorus`) holds the plugin **source** (tracked tree at `chorus-memory.plugin.src/`), the built `chorus-memory.plugin` package artifact (rebuilt on each version bump), and a credential-free A/B `eval/` harness.
 
 **1.3 in one line:** the plugin is now **user-agnostic** — the vault owner, endpoint, and API key live in a machine-local config (`~/.claude/echo-memory/config.json`), never in the source; an unconfigured machine **prompts for the key file on load** and installs it with one `config import`. Underneath: one-call `capture` routes and crosslinks memory, `recall` fuses BM25 over note bodies with graph expansion, alias-aware resolution avoids duplicate notes, and a connection-pooled client reads the whole vault concurrently. See the [version history](#version-history) for how it got here.