docs: add MIT LICENSE, AGENTS.md for development conventions, update README license section

AGENTS.md

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+# AGENTS.md
+
+Project conventions for agent-assisted development.
+
+## Project Overview
+
+This repository provides Pi coding agent skills and extensions. The primary component is **goal-driven-loop** — a skill + extension pair that keeps a session focused on a user-defined goal with explicit acceptance criteria.
+
+## Repository Structure
+
+```
+extensions/goal-driven-loop/    # TypeScript extension (Pi Extension API)
+.agents/skills/goal-driven-loop/ # Skill instructions (Markdown)
+.pi/skills/ → symlink            # Pi skill discovery
+.pi/extensions/ → symlink        # Pi extension discovery
+docs/superpowers/                # Design specs and implementation plans
+openspec/                        # OpenSpec change archive
+```
+
+Agent directories (`.claude/`, `.agents/`, `.pi/`) are **gitignored**. Only the symlinks and source files at top-level directories are committed.
+
+## Tech Stack
+
+- **Skills**: Markdown (Agent Skills standard), no build step
+- **Extensions**: TypeScript, loaded via jiti (no compilation needed), depends on `@earendil-works/pi-coding-agent` Extension API
+- **Testing**: Manual behavioral tests via `pi -p` / `pi -e`; unit tests run with `npx jiti` against individual modules
+- **Workflow**: OpenSpec → comet lifecycle for change tracking
+
+## Development Commands
+
+```bash
+# Verify skill loads
+pi -p "/skill:goal-driven-loop"
+
+# Verify extension loads
+pi -e extensions/goal-driven-loop/index.ts -p "test"
+
+# Run unit tests for trigger-detector
+npx jiti /tmp/test-trigger-detector.mjs
+
+# Run unit tests for state-injector
+npx jiti /tmp/test-state-injector.mjs
+
+# End-to-end test (create a temp project first)
+mkdir -p /tmp/test && cd /tmp/test && git init
+pi -e /path/to/pi-setup/extensions/goal-driven-loop/index.ts \
+   -p "当前目标是实现 reverseString(s) 函数"
+```
+
+## Key Design Decisions
+
+1. **Skill + Extension dual layer**: Skill = instructions (agent reads). Extension = mechanics (event handlers). Do not mix concerns.
+2. **File-based state** (`.agents/goal/GOAL.md`): Survives context compaction. Deleted on goal completion.
+3. **Extension never blocks user**: All confirms use timed auto-defaults (10s timeout). Fallbacks are safe (continue existing goal).
+4. **Anti-triggers are mechanical**: Code blocks, quote blocks, reported speech, trivial keywords — all checked programmatically, not by agent judgment.
+5. **Per-iteration retry**: Exponential backoff counter resets each iteration. 10 retries / ~37min coverage.
+6. **Comet delegation**: Coarse-grained goals auto-delegate to `comet-open`. Fallback to multi-stage mode if comet unavailable.
+
+## When Modifying This Project
+
+### Adding a new skill
+
+1. Create directory at `.agents/skills/<name>/SKILL.md`
+2. Follow the Agent Skills standard: YAML frontmatter with `name` and `description` (start with "Use when...")
+3. Keep SKILL.md ≤ 500 words; move detailed reference to `references/` subdirectory
+4. Create symlink: `ln -s ../../.agents/skills/<name> .pi/skills/<name>`
+5. Test with `pi -p "/skill:<name>"`
+
+### Adding a new extension
+
+1. Create directory at `extensions/<name>/`
+2. Write `index.ts` that exports a default function receiving `ExtensionAPI`
+3. Add `package.json` with `{ "pi": { "extensions": ["./index.ts"] } }`
+4. Create symlink: `ln -s ../../extensions/<name> .pi/extensions/<name>`
+5. Test with `pi -e extensions/<name>/index.ts -p "test"`
+
+### Modifying goal-driven-loop
+
+- **Skill layer** (`.agents/skills/goal-driven-loop/`): Changes to instructions, acceptance criteria rules, error handling reference
+- **Extension layer** (`extensions/goal-driven-loop/`):
+  - `trigger-detector.ts` — trigger phrase patterns and anti-trigger logic
+  - `state-injector.ts` — GOAL.md parsing and injection text generation
+  - `ui-prompts.ts` — timed confirms and notification helpers
+  - `index.ts` — event wiring (input, before_agent_start)
+
+After any change, re-run unit tests and E2E verification.
+
+## Commit Conventions
+
+- `feat(skill):` / `feat(ext):` — new features
+- `fix(skill):` / `fix(ext):` — bug fixes
+- `docs:` — documentation changes
+- `chore:` — maintenance (gitignore, archive, etc.)
+
+## Known Limitations (v1)
+
+1. Mid-loop granularity upgrade needs skill-side signal (`status: needs-upgrade` in GOAL.md) — extension cannot auto-detect goal complexity increase
+2. Agent "estimates < 5 min" anti-trigger is instruction-level only, not mechanical
+3. Stagnation dual-signal precise detection needs skill-side passing count history in GOAL.md — extension relies on skill's own stagnation detection

LICENSE

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+MIT License
+
+Copyright (c) 2026 Charles
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -167,4 +167,4 @@ The skill handles transient failures with exponential backoff (10 retries, ~37mi
 
 ## License
 
-MIT (assumed — please confirm with the repository owner).
+MIT — see [LICENSE](LICENSE).