test: stdio adapter dispatch, owner resolution and local env bootstrap

Cover the stdio adapter: local-mode env bootstrap (OAuth off, API-key gate off,
per-user audit path), missing-env failure, PAT owner resolution, and dispatch
(unknown tool, write-mode policy denial, and the happy path pinning request
context to the PAT owner via the shared registry). Tidy the boundary-test
assertion so ruff and black agree.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_core_boundary.py

@@ -58,7 +58,6 @@ def test_core_does_not_import_fastapi() -> None:
         capture_output=True,
         text=True,
     )
-    assert result.returncode == 0, (
-        f"core import boundary violated.\nstdout: {result.stdout}\nstderr: {result.stderr}"
-    )
+    detail = f"core import boundary violated.\nstdout: {result.stdout}\nstderr: {result.stderr}"
+    assert result.returncode == 0, detail
     assert "ok" in result.stdout