feat(plugins): ship SkillOpt-Sleep for Claude Code, Codex, and Copilot

Restructure into plugins/{claude-code,codex,copilot}/ — one engine, three thin
shells, all calling the shared plugins/run-sleep.sh -> python -m skillopt_sleep.

  - claude-code/: existing plugin moved here; runner delegates to the shared
    launcher (fixes repo-root resolution after the move).
  - codex/: ~/.codex/prompts/sleep.md custom prompt + ~/.agents/skills SKILL.md +
    install.sh + AGENTS.md hint — Codex's documented, stable extension surfaces.
  - copilot/: a stdlib-only MCP server (mcp_server.py) exposing sleep_* tools,
    plus mcp-config.example.json and a copilot-instructions snippet. Verified end
    to end (initialize -> tools/list -> tools/call returns real engine output).
  - plugins/README.md overview table; main README News + a dedicated SkillOpt-Sleep
    section; pyproject lists skillopt_sleep as a first-class package.

Decoupling emphasized throughout: open-source tool (skillopt_sleep/) with zero
dependency on the research package. 29 tests pass; all three shells resolve.

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

plugins/copilot/README.md

@@ -0,0 +1,67 @@
+# SkillOpt-Sleep — GitHub Copilot integration
+
+Give **Copilot** (CLI or VS Code) a nightly **sleep cycle** via a tiny **MCP
+server** that exposes the `skillopt_sleep` engine as tools. MCP is GitHub's
+supported way to extend Copilot, so this works across Copilot CLI, VS Code, and
+other MCP clients with the same server.
+
+## What's here
+
+| File | Purpose |
+|---|---|
+| `mcp_server.py` | stdlib-only MCP (stdio) server exposing `sleep_*` tools |
+| `mcp-config.example.json` | drop-in MCP server config |
+| `copilot-instructions.snippet.md` | paste into `.github/copilot-instructions.md` |
+
+## Install
+
+Requires Python ≥ 3.10. No third-party packages — the server is pure stdlib.
+
+1. **Register the MCP server.** Add the server to your Copilot MCP config
+   (Copilot CLI: `~/.copilot/mcp-config.json`; VS Code: your MCP settings).
+   Use `mcp-config.example.json` as a template — set `SKILLOPT_SLEEP_REPO` to
+   this repo's path:
+
+   ```json
+   {
+     "mcpServers": {
+       "skillopt-sleep": {
+         "command": "python3",
+         "args": ["/abs/path/SkillOpt-Sleep/plugins/copilot/mcp_server.py"],
+         "env": { "SKILLOPT_SLEEP_REPO": "/abs/path/SkillOpt-Sleep" }
+       }
+     }
+   }
+   ```
+
+2. **(Optional) Tell Copilot about it.** Append
+   `copilot-instructions.snippet.md` to your repo's
+   `.github/copilot-instructions.md` so Copilot reaches for the tools when the
+   user asks to "run the sleep cycle".
+
+## Use
+
+Ask Copilot things like *"run the sleep cycle"*, *"what did the last sleep
+propose?"*, *"adopt the staged sleep proposal"*. Copilot calls the MCP tools:
+`sleep_status`, `sleep_dry_run`, `sleep_run`, `sleep_adopt`, `sleep_harvest`.
+
+Each tool takes optional `project`, `backend` (`mock`/`claude`/`codex`), and
+`scope` arguments. Default backend is `mock` (no API spend).
+
+## Verify the server directly (no Copilot needed)
+
+```bash
+printf '%s\n' \
+  '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}' \
+  '{"jsonrpc":"2.0","id":2,"method":"tools/list"}' \
+  | SKILLOPT_SLEEP_REPO="$(pwd)" python3 plugins/copilot/mcp_server.py
+```
+You should see the server info and the five `sleep_*` tools.
+
+## Notes / status
+
+- MCP is the stable, official Copilot extension surface, so this is the most
+  portable of the three integrations (one server → CLI + IDE).
+- The engine and all its controls (gate on/off, multi-rollout, budget,
+  preferences, optimizer/target split) are identical across platforms — see
+  [`../../docs/sleep/CONTROLLABLE_DREAMING.md`](../../docs/sleep/CONTROLLABLE_DREAMING.md).