chore: add worktrees instructions (#96)

* chore: add .claude/worktrees/ to .gitignore

Prevents worktree directories from being accidentally staged
via git add.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore(docs): add worktree-only workflow to common mistakes in AGENTS.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: scottschreckengaust <345885+scottschreckengaust@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: scottschreckengaust

.gitignore

@@ -45,6 +45,7 @@ Handler entry tests: `cdk/test/handlers/orchestrate-task.test.ts`, `create-task.
 - **`MISE_EXPERIMENTAL=1`** — required for namespaced tasks like **`mise //cdk:build`** (see [CONTRIBUTING.md](./CONTRIBUTING.md)).
 - **`mise run build`** runs **`//agent:quality`** before CDK — the deployed image bundles **`agent/`**; agent changes belong in that tree.
 - **`prek install`** fails if Git **`core.hooksPath`** is set — another hook manager owns hooks; see [CONTRIBUTING.md](./CONTRIBUTING.md).
+- **Editing on `main` directly** — ALWAYS create a worktree with a feature branch for changes, even trivial ones. Main should stay clean; all work flows through worktree → branch → PR → merge.
 - **Git worktrees** — `node_modules/` and `agent/.venv/` are per-tree (not shared). Run **`mise run install`** in each new worktree before building. All CDK path references (`__dirname`-relative) and mise `config_roots` resolve correctly without extra setup.
 
 ### Tech stack