fix(context): accept RepositoryEntry object form in .project/ reader (closes #385)

[mlieberman85]

Summary

CNCF .project/ types.go changed Project.Repositories from []string to []RepositoryEntry in cncf/automation@bd7fec94 (2026-08-21, "feat: add RepositoryEntry type with tags and primary fields"). Each repositories[*] item may now be either a plain string OR an object of shape {url, tags?, primary?}. Feature 030's nightly canary (test_upstream_spec_unchanged) correctly fired on the drift. Without a reader reconcile, a .project/project.yaml written in the new object form degrades silently -- the pre-fix reader stores each dict item verbatim so no downstream consumer can extract the URL.

Mirrors feature 030's _coerce_scalar_or_list collapse pattern:

• New helper _coerce_repository_entry(value) -> str: returns the input for a scalar string, value['url'] for a mapping, and \"\" for anything else.
• Reader maps every item through the coercer and filters out empty results so a malformed entry (missing url) does not silently expand into a stringified representation of the mapping.
• ProjectConfig.repositories stays list[str]. Downstream consumers (dot_project_merger.py, dot_project_mapper.py) are unchanged.
• tags and primary metadata is dropped at parse time. If a future control needs the metadata, we can promote the field to a structured RepositoryEntry dataclass in a later reconcile without a further reshape.

Per feature 030 Q3: bumps DOT_PROJECT_SPEC_VERSION 1.2.0 -> 1.3.0 in lock-step with the tracked-hash file (860df23... -> afa3d179...). Module docstring's reconciliation history is extended.

Closes #385.

Side note captured in #385

tests/darnit/parity/tier1/conftest.py:32's pytest_collection_modifyitems applies the integration marker to every collected item (not scoped to tier1/), which is why unrelated PRs (e.g., #384) got gated on this upstream canary. Worth constraining that hook to items under its own conftest scope; out of scope for this PR but tracked.

Test plan

• pytest tests/darnit/context/test_dot_project.py::TestRepositoryEntryReshape -- 6 new tests pass (scalar-only, object-only, mixed, malformed-object dropped, empty-list, spec-version bump).
• pytest tests/darnit/context/test_dot_project_upstream.py -- all 5 pass on the new hash (canary now green).
• Full workspace pytest tests/ -- 2748 pass, 17 skip, 0 fail. No deselect needed.
• ruff check on touched files -- clean.
• python scripts/validate_sync.py --verbose -- PASS.

Backward compatibility: additive. Existing .project/project.yaml files with plain-string repositories items still parse to the same list[str] shape. New object-form files now also parse correctly. No downstream consumer's contract changes.