feat: add reusable-promote workflow (C1 consolidation)

[castrojo]

Summary

Consistency audit C1: consolidate promote-testing-to-main.yml from all three image repos into one reusable workflow.

Before: 875 LoC triplicated across bluefin (343) + bluefin-lts (349) + dakota (183)
After: one 220-line reusable + ~30-line callers in each image repo

Design decisions

No new secrets — uses github.token like the existing per-repo workflows. The original audit template proposed APP_ID/APP_PRIVATE_KEY but none of the existing promote workflows use an App token.

Includes the gate: job — the original template omitted this; the existing per-repo workflows all have it. It calls reusable-release-gate.yml with cosign_identity_regexp as a required input (varies per image repo).

release-state.yaml schema — kept identical to the existing per-repo format (testing: map keyed by variant name). Nothing reads this file as a pipeline input; it's a record/audit trail only. The template's proposed schema change was unnecessary.

Inputs

Input	Required	Default
variants	✅	—
cosign_identity_regexp	✅	—
registry	❌	ghcr.io/projectbluefin
run_e2e	❌	false
e2e_suite	❌	smoke
lts_floor_days	❌	0

Adoption order (canary-first)

1. dakota — 1 variant pair, lowest user impact
2. bluefin-lts — observe one promotion cycle
3. bluefin — highest user impact, land last

Adoption PRs filed separately once this merges.

Consumer validation

Consumer PR: projectbluefin/dakota#788
Consumer CI run: https://github.com/projectbluefin/dakota/actions/runs/27314334366
Out-of-org consumer impact: N/A — reusable-promote is an internal workflow called only by projectbluefin image repos. aurora and bazzite do not use promote-testing-to-main from this repo.

• Consumer PR opened and CI run linked
• CI passing (default build: success; validate job only fires on pull_request events, not workflow_dispatch — actionlint pass on this PR confirms YAML validity)
• Out-of-org impact assessed

Assisted-by: Claude Sonnet 4.5 via pi

[github-actions]

Dependency Review

The following issues were found:

• ✅ 0 vulnerable package(s)
• ✅ 0 package(s) with incompatible licenses
• ✅ 0 package(s) with invalid SPDX license definitions
• ⚠️ 1 package(s) with unknown licenses.

See the Details below.

License Issues

.github/workflows/reusable-promote.yml

Package	Version	License	Issue Type
projectbluefin/actions/.github/workflows/reusable-release-gate.yml	84649d2	Null	Unknown License

OpenSSF Scorecard

Package	Version	Score	Details
actions/actions/checkout	df4cb1c069e1874edd31b4311f1884172cec0e10	🟢 5.9	Details Check Score Reason Binary-Artifacts 🟢 10 no binaries found in the repo Dangerous-Workflow 🟢 10 no dangerous workflow patterns detected Code-Review 🟢 10 all changesets reviewed Maintained ⚠️ 2 3 commit(s) and 0 issue activity found in the last 90 days -- score normalized to 2 CII-Best-Practices ⚠️ 0 no effort to earn an OpenSSF best practices badge detected Token-Permissions ⚠️ 0 detected GitHub workflow tokens with excessive permissions Packaging ⚠️ -1 packaging workflow not detected Fuzzing ⚠️ 0 project is not fuzzed License 🟢 10 license file detected Pinned-Dependencies 🟢 3 dependency not pinned by hash detected -- score normalized to 3 Signed-Releases ⚠️ -1 no releases found Security-Policy 🟢 9 security policy file detected SAST 🟢 8 SAST tool detected but not run on all commits Branch-Protection 🟢 5 branch protection is not maximal on development and all release branches
actions/projectbluefin/actions/.github/workflows/reusable-release-gate.yml	84649d2	Unknown	Unknown

Scanned Files

• .github/workflows/reusable-promote.yml