chore(attribution): drop the one-release .claude/attribution.json team read #13476

Refs #9737

Blocked by: the ai-slop child (chore(ai-slop): drop the one-release .claude/ai-slop.json team read). Until it merges, deleting .claude/ai-slop.json makes scripts/check-purged-em-dashes.sh exit 2 (:137).

Host-run: a session pull request, for two reasons.

• It changes the /attribution:setup skill body and its eval case json-fallback-layer-moves-whole (plugins/attribution/skills/setup/evals/evals.json:107-118), which the lane cannot run.
• It deletes files under .claude/, which the lane mounts read-only (chore: drop the one-release .claude config reads and this repository's old config files #12554).

Outcome

The attribution detectors read the team and personal layers only from <home>/attribution.yaml and <home>/attribution.local.yaml. The repo-relative .claude/attribution.json and .claude/attribution.local.json fallbacks are gone. The YAML reader landed in attribution 0.12.0 (plugins/attribution/CHANGELOG.md:288-296), and 0.16.0 has shipped since.

/attribution:setup can no longer find an old JSON file through --show-config, because that file no longer appears in the Config layers list. It reports the file as a retired config instead, through the plugin's retirements.yaml and check-retirements.sh, the same way it reports .claude/provenance.json.

This repository's .claude/attribution.json and .claude/ai-slop.json are deleted. Slice 3 has made the ai-slop file unread. The user-global ~/.claude/attribution.json layer stays (lib.sh:46, ADR 0075).

Change

• plugins/attribution/skills/audit/scripts/lib.sh:53: drop the .claude/$name.json fallback, and update the comment at :34-41. Keep the user-global layer (:46) and the jq path that reads it.
• plugins/attribution/retirements.yaml: append two action: migrate records, kind: file, one with path: .claude/attribution.json and one with path: .claude/attribution.local.json. Each successor names the YAML file under the convention home. Existing records are not edited.
• plugins/attribution/skills/setup/SKILL.md:22-27,60-66:
  • Replace the "layer still on its JSON fallback" detection with the retired-config finding.
  • Keep the carry-every-key-into-the-YAML step for a found file.
  • Rewrite eval case 9 (json-fallback-layer-moves-whole) to match.
• Leave the eval samples in place:
  • plugins/attribution/evals/setup-check-writes-nothing/samples/names-team-layer.json:22 is a fail sample and stays valid.
  • The no-write-config.json samples are write-detection samples.
• Convert the test fixtures that configure a temp repo through .claude/attribution*.json: check-stamps.test.sh, list-corpus.test.sh, score-golden.test.sh, sweep-ledger.test.sh and lib.test.sh move to docs/conventions/attribution*.yaml. One case asserts that the old file is not read.
• Docs:
  • plugins/attribution/schemas/attribution.schema.json:5 description.
  • plugins/attribution/README.md:95-97.
  • plugins/attribution/skills/audit/SKILL.md:243.
  • docs/contracts/config-cascade/README.md:782.
  • The docs/conventions/attribution.yaml:2-10 header: drop the "stays until the cleanup slice", "made in both files" and "as it was in .claude/attribution.json" text.
• Delete .claude/attribution.json, and .claude/ai-slop.json once slice 3 has merged.
• Run the attribution setup eval cases before and after the change, and put the result in the pull request.
• Add an attribution changelog fragment.

Done when

• git ls-tree --name-only HEAD .claude/attribution.json .claude/ai-slop.json prints nothing.
• git grep -nP '(?<!~/)(?<!HOME/)(?<!\}/)\.claude/(attribution(\.local)?\.json|\$name\.json)' -- plugins/attribution docs/conventions/attribution.yaml docs/contracts ':!*CHANGELOG*' ':!*.test.sh' ':!plugins/attribution/evals' ':!plugins/attribution/retirements.yaml' ':!plugins/attribution/skills/setup/evals' prints nothing (on origin/main it prints 7 lines in 4 files).
• git grep -nE 'JSON fallback|\.claude/. JSON|its \.claude/attribution\.json fallback|still on its fallback' -- plugins/attribution ':!*CHANGELOG*' ':!plugins/attribution/retirements.yaml' prints nothing (on origin/main it prints 11 lines in 4 files).
• grep -n '^## \[0.13.0\]' plugins/attribution/CHANGELOG.md prints one line (a release after the 0.12.0 YAML reader).
• bash scripts/check-purged-em-dashes.sh exits 0.
• git grep -n 'path: .claude/attribution.json' -- plugins/attribution/retirements.yaml prints one line.
• git grep -n 'cfg_layer_add "${HOME:-/nonexistent}/.claude/attribution.json"' -- plugins/attribution/skills/audit/scripts/lib.sh prints one line (the user layer stays).
• bash scripts/run-test-file.sh plugins/attribution/skills/audit/scripts/lib.test.sh exits 0.
• bash scripts/run-test-file.sh plugins/attribution/skills/audit/scripts/check-stamps.test.sh exits 0.
• bash scripts/run-test-file.sh plugins/attribution/skills/audit/scripts/list-corpus.test.sh exits 0.
• bash scripts/run-test-file.sh plugins/attribution/skills/audit/scripts/score-golden.test.sh exits 0.
• bash scripts/run-test-file.sh plugins/attribution/skills/audit/scripts/sweep-ledger.test.sh exits 0.
• scripts/check-changelog-fragments.sh --check-required origin/main exits 0.