feat(pi): add persistent Mosaic goal controller

packages/mosaic/framework/defaults/README.md

@@ -94,7 +94,14 @@ The launcher:
 1. Verifies `~/.config/mosaic` exists
 2. Verifies `SOUL.md` exists (auto-runs `mosaic init` if missing)
 3. Injects `AGENTS.md` into the runtime
-4. Forwards all arguments to the runtime CLI
+4. For Pi, loads the framework-owned core and persistent-goal extensions from
+   `~/.config/mosaic/runtime/pi/`
+5. Forwards all arguments to the runtime CLI
+
+Inside `mosaic pi`, `/goal set <statement>` starts a bounded persistent goal loop. Use `/goal status`,
+`/goal pause`, `/goal resume`, or `/goal cancel` to control it. The extension remains part of Mosaic
+under `~/.config/mosaic/runtime/pi/goal-extension.ts`; it is not installed in Pi's main extension
+directory.
 
 You can still launch runtimes directly (`claude`, `codex`, etc.) — thin runtime adapters will tell the agent to read `~/.config/mosaic/AGENTS.md`.
 
@@ -114,7 +121,7 @@ You can still launch runtimes directly (`claude`, `codex`, etc.) — thin runtim
 │   ├── claude/            ← CLAUDE.md, RUNTIME.md, settings.json, hooks
 │   ├── codex/             ← instructions.md, RUNTIME.md
 │   ├── opencode/          ← AGENTS.md, RUNTIME.md
-│   ├── pi/                ← RUNTIME.md, mosaic-extension.ts
+│   ├── pi/                ← RUNTIME.md, mosaic-extension.ts, goal-extension.ts
 │   └── mcp/               ← MCP server configs
 ├── skills/                ← Universal skills (synced from mosaic/agent-skills)
 ├── skills-local/          ← Local cross-runtime skills
@@ -126,7 +133,7 @@ You can still launch runtimes directly (`claude`, `codex`, etc.) — thin runtim
 
 | Launch method       | Injection mechanism                                                                       |
 | ------------------- | ----------------------------------------------------------------------------------------- |
-| `mosaic pi`         | `--append-system-prompt` with composed runtime contract + skills + extension              |
+| `mosaic pi`         | `--append-system-prompt` with composed runtime contract + skills + Mosaic extensions      |
 | `mosaic claude`     | `--append-system-prompt` with composed runtime contract (`AGENTS.md` + runtime reference) |
 | `mosaic codex`      | Writes composed runtime contract to `~/.codex/instructions.md` before launch              |
 | `mosaic opencode`   | Writes composed runtime contract to `~/.config/opencode/AGENTS.md` before launch          |