docs: rewrite AGENTS.md with conventional commits and lean guidance (#13)

## Summary
- Rewrites AGENTS.md from a 14-line CLAUDE.md duplicate into a lean,
agent-focused guide (~19 lines)
- Adds Conventional Commits guidance (requested in #7 by @alecthomas)
- Adds `just run` and `just test-one` recipes to Justfile so all
commands live in one place
- Adds gotchas (consolidate into KNOWN_AGENTS, keep it fast) and a
self-improving maintenance line

## Test plan
- [x] `just lint` passes
- [x] `just test` passes (all 20 tests)
- [ ] Review AGENTS.md content for completeness and tone

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: baldawarishi

AGENTS.md

@@ -1,13 +1,18 @@
-This is a Rust project.
+This is a Rust project. Hermit manages toolchains, Just manages commands.
 
-The script ./scripts/aittributor is a convenience script that compiles and executes aittributor. ALWAYS use this to run, NEVER manually compile and run.
+Run `just` to see all available commands. Use `just run` to build and run — NEVER manually compile and run. Use only libraries already in Cargo.toml.
 
-We use:
-- Hermit to manage toolchains and tools.
-- Just for command running.
+README.md describes the design of this command-line tool. ALWAYS keep it up to date with features.
 
-Use the libraries already added in @Cargo.toml.
+## Commits and PRs
 
-@README.md describes the design of this command-line tool.
+Use Conventional Commits for commit messages and PR titles. CI lints PR titles.
 
-ALWAYS keep the README up to date with features.
+## Gotchas
+
+- Consolidate all agent data into `KNOWN_AGENTS` in `src/agent.rs`.
+- This tool runs on every commit — keep it fast (1-second hard timeout).
+
+## Maintenance
+
+You may update this file to correct mistakes.

Justfile

@@ -14,10 +14,18 @@ fmt:
 build:
     cargo build --release
 
+# Build and run aittributor
+run *ARGS:
+    ./scripts/aittributor {{ARGS}}
+
 # Test the project
 test:
     cargo test --all-features
 
+# Run a single test by name
+test-one NAME:
+    cargo test {{NAME}} --all-features
+
 # Generate release notes from git log since previous tag
 release-notes tag="":
     #!/usr/bin/env bash