10x-implement branching: conventional names, squash lifecycle, trailer ledger

What

Rework 10x-implement's runtime branching in target repos: conventional branch names, squash-only integration and landing, durable trailer ledger, monitoring cheat-sheet. Design agreed in a grilling session on 2026-09-04.

Naming grammar

• <type> from the closed list feat fix docs refactor perf test chore; the spec's primary type headlines the landing commit.
• <spec> / <slug>: kebab-case, ASCII, ≤30 chars; slug stable across rounds (name reused, branch re-created per round).
• No 10x/ prefix in branch names; the skill's fingerprint moves to commit trailers (git log --grep='^10x-').

Lifecycle (squash twice)

1. Create worktree + branch per chunk
2. Coder: small TDD commits on the chunk branch
3. Merger: round 1 checkout -B integrate/<spec> <base> (never reset after), git merge --squash per chunk in dependency order → one commit per chunk, subject <type>: <summary> (round <n>), trailer 10x-chunk: <type>/<spec>/<slug>
4. Gates; cleanup for clean+passing chunks: worktree remove + branch -D
5. Reviewer: git diff <base>...integrate/<spec>
6. Ship (orchestrator): checkout <base> && merge --squash integrate/<spec> → landing commit → branch -D integrate/<spec>

Landing commit (the only durable survivor)

<type>(<spec>): <run summary>

10x-chunk: <type>/<spec>/<slug> · round <n> · check: <result>
10x-round: <n> · hard findings: <k> → <slugs>

10x-spec: <spec>

Files

• skills/10x-implement/references/BRANCHING.md (new): grammar, lifecycle, templates, cheat-sheet
• skills/10x-implement/SKILL.md: multiplier 3, Setup, Decompose (spec/type), Merge, Review, new Ship step, fallback branch
• agents/10x-coder.md, agents/10x-merger.md (squash sequence, -D cleanup, chunk template), agents/10x-reviewer.md
• Re-run scripts/install.py

Start with skills/10x-implement/references/BRANCHING.md and skills/10x-implement/SKILL.md, then compare the requested lifecycle with agents/10x-coder.md, agents/10x-merger.md, and agents/10x-reviewer.md. Update the named files for branch grammar, squash integration and landing, trailers, cleanup, and the Ship step, then re-run scripts/install.py.