Adopt PR-flow dogfooding: every change lands through its own receipt

[joshft]

Makes the CI receipt the real merge path instead of a bystander: this is the first PR the workflow has ever run on.

• Ignore /receipt.md and /receipt.json — the CI shell redirect creates the receipt file before the scanner walks the tree, so an unignored receipt would appear inside its own change scope as an untracked file.
• Append the receipt to the job summary.
• Record the convention in AGENTS.md: no direct commits to master; the receipt is read before merge; refutations block; a remainder that misstates the change is itself a correctful bug the PR surfaced.

What the receipt cannot check here, and why that is acceptable: the change is docs + config (.gitignore, workflow YAML, AGENTS.md) — no harvester exists for those surfaces, and the receipt discloses them as unread rather than claiming coverage it does not have.

🤖 Generated with Claude Code

https://claude.ai/code/session_015GeUG1gboWiZSnFyzQghyp

[github-actions]

correctful receipt

0 claims — ✅ 0 verified · ❌ 0 refuted · ⚠️ 0 unverified

Change: origin/master...HEAD (e1a2774..61d757d) — 3 files

⚠️ Unverified remainder (0) — what nothing checked

Empty — every harvested claim reached a probe.

Harvest coverage: 3 files — 0 claimed · 1 scanned · 2 unread
_{unread (no harvester for): .gitignore×1 .yml×1}

_{schema 0.0.4 · exit gate: refuted claims block; the remainder informs, never fails}