Aireceipts

Minor: PR receipts can now attach and post themselves. A receipt travels with the
branch as a sibling git ref and CI renders + posts the comment, so a receipt lands even
when no one runs pr --post. Rendered receipt output is unchanged from v0.3.0 (goldens
byte-identical); the new surface is opt-in.

Added

• Seamless PR receipts — store=ref + pre-push hook (SPEC-0065): aireceipts pr --store ref (or AIRECEIPTS_STORE=ref) writes the receipt as a deterministic git
  object on refs/receipts/<slug> — invisible in the tree and PR diff, byte-identical
  across machines (dated from the session's own endedAt, never wall-clock). A committed
  .githooks/pre-push hook generates and pushes that ref on git push (best-effort;
  never blocks a push, no second push). npm run setup:hooks activates the hook for a
  clone of this repo; the default store stays comment.
• CI posts the receipt from the ref (SPEC-0066): a two-job pr-receipt-check.yml
  fetches the branch ref, validates and sanitizes the untrusted, fork-author-controlled
  payload, renders it through the existing renderer, and upserts one marker comment via
  GITHUB_TOKEN — no local gh required. Opt-in enforcement
  (AIRECEIPTS_REQUIRE_PR_RECEIPT=true) makes same-repo PRs require a receipt; fork
  PRs always stay notice-only (their transcripts live on the contributor's machine, so CI
  can't generate one). Enforcement is currently coarse — it does not yet distinguish
  agent-built from hand-written PRs.
• @latest distribution pin (SPEC-0064 R1): the PR-receipt-check caller installs the
  reusable workflow at @latest; the moving latest git tag is advanced by the release
  workflow on each publish. (SPEC-0064 R2–R4, the npm-native pr-check command, remain in
  progress.)

Performance

• Faster feedback (SPEC-0063): in-process sqlite parsing, a goldens compile cache, and
  parallel preflight reduce CLI and preflight wall-clock.

Security

• The receipt payload that rides on the branch ref is treated as untrusted input — anyone
  who can push a branch, including a fork author, controls its bytes. The CI post path is a
  hardened trust boundary: a field-aware sanitizer (bracket-escape +
  autolink defang for live-markdown fields, fence-guard for fenced text, an
  https-allowlist that rejects markdown-breaking characters for artifact URLs), rendered in
  a token-less render job whose data-only artifact is posted by a separate post
  job — golden-gated against an injection corpus.

Docs

• Adopter kit: a minimally-invasive default plus opt-in tiers for repos that want to turn
  enforcement up (docs/pr-receipts.md, docs/adopt/).