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

uv.lock

@@ -465,8 +465,8 @@ wheels = [
 
 [[package]]
 name = "llm-ingestion-okf"
-version = "0.1.0"
-source = { git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git?rev=dae0bd1a2898b69f436a877538d67afd71e48ad8#dae0bd1a2898b69f436a877538d67afd71e48ad8" }
+version = "0.3.1"
+source = { git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git?rev=v0.3.1#692f2df2ba5aa160810b126dab3574cd297218b9" }
 
 [[package]]
 name = "mcp"
@@ -608,7 +608,7 @@ dev = [
 [package.metadata]
 requires-dist = [
     { name = "claude-agent-sdk", specifier = ">=0.2.111,<0.3" },
-    { name = "llm-ingestion-okf", git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git?rev=dae0bd1a2898b69f436a877538d67afd71e48ad8" },
+    { name = "llm-ingestion-okf", git = "https://git.fromaitochitta.com/open/llm-ingestion-okf.git?rev=v0.3.1" },
     { name = "pydantic", specifier = ">=2" },
 ]