parallel-sessions-protocollisted

# Parallel Sessions Protocol Keep any number of parallel sessions on one repository from trampling each other, without capping how many run. Field-proven under real load: one day of 7 simultaneous worktrees and 8 merged PRs produced six distinct collision incidents; every mechanism below exists because one of them happened. Posture: guarded-mutation — this skill creates branches and draft PRs; merging stays governed by each project's own authorization rules. **Preconditions**: a git repository with a GitHub remote and an authenticated `gh` CLI (`references/setup-guide.md`). If either is missing, say so and stop — the board mechanism cannot work without them. **Core model**: one track = one session + one branch + one exclusive working directory + one claim declaration. Sharing a working directory across sessions is the root cause of cross-track pollution — never do it. The number of tracks is unbounded; the constraint is behavior, not count. ## Mechanism 1 — Register before you code (the board) Before writing any code: 1. `git fetch origin` and `gh pr list --state open` — see the whole board first. 2. Branch from **latest** `origin/main`; take an exclusive working directory (the main checkout counts as one — at most one session may own it at a time; every other session uses its own worktree). 3. Immediately open a **draft PR** whose body has three fixed sections (template in `references/draft-pr-template.md`): - **Claimed scope** — directories/files this trac