chore(deps): re-pin llm-ingestion-okf to v0.3.1 + migrate tests to stable error codes

Pin dae0bd1a -> v0.3.1 (=692f2df) on the public Forgejo mirror; uv.lock pins
the exact commit behind the tag.

- Drop the mypy override: the library ships py.typed from v0.2.0, so strict
  mode now follows its real types instead of follow_untyped_imports.
- Migrate 8 library-error assertions from pytest.raises(match=...) to
  exc.value.code — message text is explicitly unstable from v0.3.0, the
  codes are the stability contract.
- Fix a real breakage the bump surfaced: IngestResult gained a required
  `stamp` field (d3a3bcc), which the delegation fake did not construct.
- The read-only SQL test loses resolution under the code contract
  (`sql_failed` is generic), so it now proves read-onlyness by effect —
  the write never lands — instead of by message wording.
- Correct the guard plan: G1's persist-gate anchor (ingest.py:372-387) died
  with the 2026-07-16 adoption. Door A is ungated by the library's own
  README, so gating stays our responsibility at the call site.

Verified: 426 tests green, golden output byte-exact unchanged, full gate
clean (ruff + format + mypy strict).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RmNAgbRXUgvoSKxVK4Bevv

pyproject.toml

@@ -12,10 +12,10 @@ dependencies = [
 
 # Distribution channel (2026-07-16 decision, mirrors the library's B2 answer):
 # git pin against the public Forgejo repo — reproducible for every consumer of
-# this public repo, uv.lock pins the exact commit. Bump the rev to the release
-# tag once the library tags one.
+# this public repo, uv.lock pins the exact commit behind the tag. Bump the rev
+# when the library releases a new tag.
 [tool.uv.sources]
-llm-ingestion-okf = { git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git", rev = "dae0bd1a2898b69f436a877538d67afd71e48ad8" }
+llm-ingestion-okf = { git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git", rev = "v0.3.1" }
 
 [dependency-groups]
 dev = [
@@ -38,11 +38,5 @@ target-version = "py310"
 [tool.mypy]
 strict = true
 
-# llm-ingestion-okf ships full inline type hints but (as of 0.1.0 @ dae0bd1a)
-# no py.typed marker; follow its inline types instead of degrading to Any.
-[[tool.mypy.overrides]]
-module = "llm_ingestion_okf.*"
-follow_untyped_imports = true
-
 [tool.pytest.ini_options]
 testpaths = ["tests"]