fix(storage): ignore invalid ancestor Git markers

[faga295]

Summary

Ignore structurally invalid .git entries in strict ancestors when classifying a selected folder, while preserving fail-closed behavior for a malformed .git entry in the selected folder itself. Valid Git directories, gitdir: indirection files, repositories, and linked worktrees continue to resolve normally.

Add regression coverage for Project Catalog classification and workspace identity marker publication.

Fixes #4806

Verification

• npm --workspace @maka/storage run build
• npm --workspace @maka/storage run typecheck
• npm --workspace @maka/storage run test:dist — 1,112 passed, 8 skipped, 0 failed
• npx biome check packages/storage/src/git-entry.ts packages/storage/src/__tests__/project-catalog.test.ts packages/storage/src/__tests__/workspace-identity.test.ts
• npm run check:asf-headers
• Verified the affected real-world folder now resolves with kind: 'folder'

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: OpenAI Codex — root-cause analysis, implementation, regression tests, verification, and PR drafting.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[hqhq1025]

I found one correctness gap in the ancestor-marker validation. The patch fixes the reported missing-HEAD shape, but other structurally invalid ancestor markers still enter the Git path and fail project/workspace resolution. The exact-head build, Storage typecheck, full Storage suite (1,113 passed, 10 skipped), Biome, ASF header audit, diff check, and a patch-preserving merge onto current main passed. GitHub currently exposes only the label check for this head.

Automated review notice: This comment was posted by an automated review agent operated by hqhq1025. It is not an independent human review and does not replace one.

[hqhq1025]

[P2] Validate the Git metadata rather than only the existence of HEAD. pathExists() returns true for any stat-able path, so an ancestor whose .git/HEAD is a directory or contains garbage, and even a repository missing objects or refs, still passes this branch. On this exact head I reproduced all four cases: hasEnclosingGitEntry() returned true, then resolveProjectLocation() exited with Git code 128 and resolveWorkspaceIdentity() returned workspace_io_failed. A gitdir: target with a garbage HEAD fails the same way. The new tests cover only the no-HEAD fixture, so the advertised invalid-ancestor behavior remains incomplete. Please validate enough of the Git directory/gitfile contract to reject these shapes and add regression coverage for at least malformed/non-regular HEAD.