Automate Superpowers upgrade pull requests

[rochecompaan]

Summary

• Added a dedicated Superpowers release discovery/update library and transactional updater CLI.
• Added Git-independent tracked-file snapshots/rollback and repository-wide Superpowers consistency contracts.
• Added an independent daily/manual Superpowers dependency upgrade workflow that validates before minting the automation App token and opening review-gated PRs.
• Documented independent Pi and Superpowers dependency upgrade workflows.

Validation

• node --test scripts/superpowers-upgrade-lib.test.mjs scripts/tracked-files.test.mjs scripts/update-superpowers.test.mjs scripts/superpowers-repository-contract.test.mjs src/workflow/skill-pack.test.ts — 37/37 passing.
• npm test — 1,243/1,243 passing.
• node scripts/smoke-packed-artifact.mjs — passed.
• npm run lint — passed.
• npx prettier --check .github/workflows/superpowers-upgrade.yml — passed.
• nix run nixpkgs#actionlint -- .github/workflows/superpowers-upgrade.yml — passed.
• Validate-only scheduled updater and git diff --exit-code — passed, no tracked diff.
• npm dependency hash freshness and nix build .#patchmill --print-build-logs — passed.

Reviews

• Final Codex full-worktree review loop passed after accepted fixes.
• Final thermo-nuclear full-worktree review passed.
• Final validation-readiness review passed all required commands.

Closes #139

Patchmill run cost

Stage	Model	Prompt tokens	Output tokens	Estimated cost (USD)
Development environment	gpt-5.5	456,708	1,859	$0.6413
Implementation	gpt-5.5	2,567,604	14,087	$2.3811
Implementation	gpt-5.6-sol	5,152,335	83,854	$8.7394
Implementation	gpt-5.6-terra	5,395,262	35,444	$2.6934
Implementation subtotal		13,115,201	133,385	$13.8139
Total		13,571,909	135,244	$14.4551

Prompt tokens include uncached input, cache reads, and cache writes. Cost is an estimate based on Pi's recorded model pricing and includes parent and subagent sessions.