docs(agents): add git fetch instruction before worktree creation (#102)

Ensures new worktrees branch from the latest remote main rather than
a potentially stale local ref. This prevents PRs from being based on
outdated commits.

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

Author: scottschreckengaust

AGENTS.md

@@ -46,7 +46,7 @@ Handler entry tests: `cdk/test/handlers/orchestrate-task.test.ts`, `create-task.
 - **`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.
+- **Git worktrees** — Always **`git fetch origin main`** before creating a new worktree to ensure you branch from the latest remote state. `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