Make the loop contract machine-checked and the contributor path obvious

[AetherAI3]

What changes, and what failure made it necessary

The catalog reached 21 loops with nothing checking that a loop file follows the contract it claims to follow. Frontmatter shape, section order, and README coverage were conventions held up by review attention. A contributor had 18 lines of CONTRIBUTING.md, no local check, and no way to know their file was correct before opening a PR.

That gap had already produced drift: the loop-cards graphic was titled "The 15 Agentic Loops" while the repo shipped 21, the README catalog table listed only the base 15 (LOOP-16 through LOOP-21 were reachable through prose links alone), and the stars badge, made-by badge, and footer all still pointed at the pre-rename DBarr3 namespace.

Landed

• tools/validate_loops.py — standard-library validator for the PROTOCOL.md §14 contract. Checks frontmatter keys and values, filename/loop-id/name agreement, all eleven sections present and in order, a fenced RUN PROMPT, duplicate ids, non-portable paths, composed-of references, README catalog coverage, and every relative markdown link in the repo. No install step, so what CI runs is exactly what a contributor runs on a fresh clone.
• .github/workflows/validate.yml — runs that single command on push and PR.
• Issue forms for the three real contribution shapes: a RUN PROMPT that broke, an improvement to an existing loop, a new-loop proposal. The bug form asks which agent and model (otherwise "it did not work" is unreproducible) and whether the loop exceeded its declared risk class, which jumps the queue.
• PR template carrying run notes and the safety boundary.
• CONTRIBUTING.md rewritten from 18 lines into an actual path: pick a contribution, the contract in short, the five safety requirements and why each exists, how to test a prompt, and explicit permission to write "not run, docs only" rather than tick a box falsely.
• PROTOCOL.md §14 now documents read-only→branch (four shipped loops already use it), the parenthetical scope-note form (branch-mutating (loops only)), and composed-of.

Validation

• python tools/validate_loops.py passes locally — 21 loops conform to PROTOCOL.md section 14.
• I ran the changed RUN PROMPT against a real repo with a real agent

Not run — no RUN PROMPT or loop behavior changed in this PR. It is tooling, templates, and documentation only.

The validator itself was tested in both directions rather than only written: against the clean catalog (exit 0, 21 loops), and against a deliberately broken probe file, which it rejected with the expected six violations — wrong loop-id for its filename, wrong name slug, an invented risk-class, a missing # Adversarial Check section, an absolute /Users/... path, and a duplicate loop-id. All five issue forms and the workflow parse as YAML.

Safety boundary

• The loop stays inside its declared risk-class — no loop behavior changed
• Nothing merges to a default branch without operator approval
• No project-specific paths, hostnames, tool names, or infrastructure assumptions were introduced

CONTRIBUTING.md now states the safety rules explicitly (least-invasive risk class, no default-branch merges inside a loop, checkpointed mutations, an adversary that can actually FAIL, FAIL-with-artifact over silent success) so that a contributor cannot weaken one without noticing.

For a new loop only

Not applicable — no loop added.

🤖 Generated with Claude Code

[AetherAI3]

Rebased the branch to drop the DBarr3 → AetherAI3 badge and footer edits — #6 owns that change, and carrying it here would only produce a conflict for whichever merges second. New links added by this PR (the issue-template config, the good first issue pointer in the README) already use the canonical namespace, so no follow-up is needed once #6 lands.

Merge order does not matter now; the two PRs no longer touch the same lines.