fix(automerge): gate .github/dependabot.yml + composite actions as risk-tier

[topcoder1]

Problem

The claude-author-automerge risk-tier regex covered .github/workflows/** but not the sibling non-workflow .github/ surfaces. On 2026-07-10 ~15:13 UTC six Claude-authored PRs whose ONLY change was .github/dependabot.yml (+2/−2) auto-merged fleet-wide:

• topcoder1/attaxion_marketing#18, topcoder1/basecamp-mcp#32, topcoder1/hr-center#20
• whois-api-llc/wxa-secrets#23, whois-api-llc/wxa_marketing#41, whois-api-llc/wxa_sanctions#27

This contradicts the CLAUDE.md policy classifying .github production-infra config as manual click-merge.

Fix — enumerate, don't blanket

Per the 2026-05-24 lesson ("automerge risk-tier globs are literal-segment alternations"), a blanket .github/** would wrongly sweep in README-ish files. So the added coverage is enumerated:

Pattern	Why
^\.github/dependabot\.ya?ml$	dependency-automation config (controls what auto-merges; can set insecure-external-code-execution)
^\.github/actions?/.*	repo-local composite actions, singular or plural (executed CI code)
^\.github/scripts/.*	workflow-invoked scripts (executed CI code)
(^|/)action\.ya?ml$	GitHub's reserved action-def filename, gated at any depth — like the existing Dockerfile/main.go/.sql filename rules — so actions outside .github/action(s)/ are still caught

Kept auto-mergeable (pinned SAFE in the corpus): .github/ISSUE_TEMPLATE/, PULL_REQUEST_TEMPLATE.md, FUNDING.yml, actionlint.yml, root dependabot.yml, and reaction.yaml/transaction.yml filename lookalikes.

Lockstep (no drift)

• This PR: global regex in claude-author-automerge.yml, its mirror in selftest/test_automerge_risk_patterns.sh, the shared selftest/risk_patterns_corpus.txt (RISKY + SAFE, read by both GH and BB selftests), and this repo's .github/risk-paths.yml classifier.
• dotclaude (separate, local): bb-automerge.py HIGH_RISK_PATTERNS, the CLAUDE.md Claude-authored-PR policy + 2026-05-24 lesson, and install-automerge-policy.sh prose.

Verification

• GH selftest ✅ + BB selftest ✅ (166 corpus cases)
• Full uv run pytest -q ✅ (7 passed)
• classify.mjs functionally confirmed: dependabot.yml→blocked, action(s)/→sensitive, actionlint.yml/ISSUE_TEMPLATE/root-dependabot.yml→non-risk
• Codex pre-review: 6 rounds, converged clean (each round hardened the action-location coverage; closed permanently via the reserved-filename rule)

Auto-merge rationale: MANUAL — touches .github/workflows/** (risk-tier) and PRs to topcoder1/ci-workflows are always manual click-merge. Auto-merge intentionally NOT enabled.

🤖 Generated with Claude Code

[github-actions]

Risk class: blocked — manual merge required.

This PR touches one of the blocked path categories from .github/risk-paths.yml (Dockerfiles, docker-compose, .github/workflows/**, **/.env*, **/secrets*, infra/, terraform/, k8s/, or the classifier config itself).

Auto-merge is refused by claude-author-automerge.yml. A maintainer should review the diff and click "Squash and merge" themselves.

(This is a policy notice, not a code-quality failure. The classify job itself does not fail — required CI checks remain authoritative for "is the code green.")

[github-actions]

Coverage Floor — mode: enforce

metric	value
measured	100.0%
floor (current)	99.0%
target	100.0%
last bumped	2026-05-12

[claude]

No issues found. Regex additions are correctly anchored, consistent across the workflow/selftest/corpus, and covered by new RISKY+SAFE corpus cases (incl. lookalikes like reaction.yaml/actionlint.yml/root-dependabot.yml).