build-executor

# Build Executor Controls the implementation phase. Uses `execution-contract.md` as the workflow authority. ## Required Inputs For Full or legacy Hotfix, read `execution-contract.md`, `tasks.md`, relevant `specs/`, and relevant `design.md`. Quick, direct incident Hotfix, and Tweak require only their receipt, request boundary, changed files, and verification command. Check workflow mode and receipt first. Tweak → direct edit mode. Quick or a valid direct incident Hotfix → Direct Quick and Hotfix. Full or legacy Hotfix → standard contract-first discipline. Branch/worktree preflight before ANY implementation edit (mandatory — do not skip): 1. Run the isolation check: ```bash ssf isolate <change-dir> ``` This script enforces git isolation: if you are on `main`/`master` it creates a git worktree (preferred) or a new branch, and exits non-zero if it cannot and you have not approved `--force`. 2. If `ssf isolate` exits non-zero: STOP. Do not edit `main`/`master` in place. Ask the user for explicit approval (and re-run with `ssf isolate <change-dir> --force` only after they approve). 3. If it succeeds, report the chosen branch/worktree and make all implementation edits there. ## Core Laws ### Law 1: Contract First (Full and legacy Hotfix) For Full and legacy Hotfix, the execution contract is the approved handoff artifact, not chat history. Direct Quick and incident Hotfix use their valid direct receipt plus bounded verification instead; they must not...