feat(ci): manifest-aware dependency PRs and cleanup protection

Implements: DEVX-165 REQ-1..3

- create_dependency_pr gains --manifest/--verify-container/--source-ref:
  resolves the producer image's OCI digest via the packages API before
  opening the PR, then writes structured manifest fields
  (version/git_ref/image_tag/image_digest/updated_at) in the PR branch
- clean_images gains --protect: pinned versions survive --keep trimming
  so a manifest-referenced digest can't be garbage-collected
- regression tests for digest resolution, manifest helpers, verify
  ordering, and protect filtering

docs/specs/DEVX-165.md

@@ -1,31 +1,55 @@
-# DEVX-165: Accept deps: as valid conventional commit type
+# DEVX-165: Manifest-aware dependency PRs and registry cleanup protection
 
 ## Problem
-The commit validator rejects `deps:` as a conventional commit type, causing
-post-merge CI failures on grm and sso-bridge repos where automated dependency
-bump PRs use `deps: bump devx...` as the commit message.
+
+S03 (OBL-INFRA-548 REQ-3) requires an immutable delivery contract: infra
+pins the sso-bridge release as {version, git ref, image tag, OCI digest}
+in a JSON manifest. Two gaps in devx block that:
+
+1. `create_dependency_pr` only regex-bumps a version string in
+   pyproject/ansible vars — it cannot update a structured manifest with
+   the resolved image digest, and it does not verify the producer
+   artifact exists before opening the PR.
+2. `clean_images` deletes all but the newest N tags — a tag/digest that
+   infra still pins gets deleted once newer releases land, breaking
+   deploys.
 
 ## Approach
-REQ-1: Add `deps` to `CONVENTIONAL_RE` in `src/devx/config.py`
-REQ-2: Update the allowed types list in the error message in
-  `src/devx/ci/validate_commit_msg.py`
-REQ-3: Add test coverage for `deps:` type in `tests/unit/test_config.py`
-  and `tests/unit/test_validate_commit_msg.py`
+
+REQ-1: `create_dependency_pr` gains `--manifest <path>` +
+`--verify-container <owner/name>`: before opening the PR it resolves the
+container tag's OCI digest via the registry `manifests` API
+(`Docker-Content-Digest`), then updates manifest fields
+`{version, git_ref, image_tag, image_digest, source_commit, updated_at}`
+in the PR branch instead of a regex bump.
+
+REQ-2: `clean_images` gains `--protect` (repeatable): named versions are
+never deleted regardless of `--keep` trimming.
+
+REQ-3: Regression tests for manifest update, digest resolution,
+verify-then-PR ordering, and protect filtering.
+
+## Files Affected
+
+- `src/devx/ci/create_dependency_pr.py`
+- `src/devx/tools/clean_images.py`
+- `tests/unit/test_create_dependency_pr.py`
+- `tests/unit/test_clean_images.py`
 
 ## Test Plan
-- `make pytest-cov` passes with 100% coverage
-- `make lint-all` passes
+
+- New unit tests per REQ; `make pytest-cov`, `make lint-all`.
 
 ## Deploy Plan
-- Merge to master → post-merge auto-publishes new devx version
-- grm and sso-bridge bump devx version to pick up the fix
+
+- Merge → devx release → consumer repos pick up via dependency PRs.
 
 ## Rollback Plan
-- Revert the merge commit
+
+- Revert; regex version bump and unprotected cleanup return.
 
 ## Acceptance Criteria
-- [x] REQ-1: Add `deps` to `CONVENTIONAL_RE` in `src/devx/config.py`
-- [x] REQ-2: Update the allowed types list in the error message in
-  `src/devx/ci/validate_commit_msg.py`
-- [x] REQ-3: Add test coverage for `deps:` type in `tests/unit/test_config.py`
-  and `tests/unit/test_validate_commit_msg.py`
+
+- [x] REQ-1: Manifest update + pre-PR OCI digest verification
+- [x] REQ-2: `--protect` exempts versions from cleanup
+- [x] REQ-3: Regression tests added and passing