docs: add Global LLM Worktree Rule to operating rules (#272)

Require mutations only from branches/ worktrees after proving project
root, cwd, branch, stable main-checkout branch, and session worktree
path. Surface in portable skill, runbooks, wiki, operator guide, and
start-issue template.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/wiki/Operator-Guide.md

@@ -13,6 +13,7 @@ Handbook for LLM operators and human developers using the Gitea-Tools MCP server
 3. **One unit of work per session** — Implement one claimed issue *or* review/merge one PR; do not mix author and reviewer mutations in one session.
 4. **No self-review / no self-merge** — The authenticated Gitea user must not approve or merge a PR they authored.
 5. **Follow the gates** — Prompts express intent; MCP tools enforce safety. Never bypass gates via prompt instructions.
+6. **Global LLM Worktree Rule** — Main checkout stays on `master`/`main`/`dev`; all mutations happen under `branches/`. Prove project root, `cwd`, branch, stable main-checkout branch, and session worktree path before editing. No exceptions.
 
 ## Supported Gitea instances
 

docs/wiki/Workflow.md

@@ -17,6 +17,9 @@
 0. Work Selection Rule — verify a work lease before any mutations (open PRs,
    issue-linked PRs, branches, worktrees, dirty worktrees, active leases/
    handoffs, merged-PR completion). Stop if another session owns the lease.
+0b. Global LLM Worktree Rule — main checkout on `master`/`main`/`dev` only;
+   mutate only from a `branches/` worktree after proving root, cwd, branch,
+   stable main-checkout branch, and session worktree path (no exceptions).
 1. `gitea_resolve_task_capability` for the author task.
 2. `gitea_lock_issue` before implementation mutations.
 3. Claim with `gitea_mark_issue` / `status:in-progress` label.