fix: remove coverage context table to fix xdist worker crash

- Remove --cov-context=test from CI pytest command
- Remove context = test from pyproject.toml [tool.coverage.run]
- Fix signed_approval.py conditional import for mypy pre-commit

The SQLite 'context' table created by coverage's per-test context
feature races under xdist parallel workers, producing:
  sqlite3.OperationalError: no such table: context
This kills the xdist worker, cascading into 800+ test errors.

Constraint: coverage --cov-context=test is incompatible with xdist -n auto
Tested: ruff, bandit, mypy (source+tests), audit_test_quality, audit_config_access, smoke test tier
Confidence: high

Author: johnteee

.github/workflows/ci.yml

@@ -138,7 +138,7 @@ jobs:
         env:
           PYTHONHASHSEED: "0"
         # Use xdist -n auto to parallelize and avoid OOM on GH runners
-        run: pytest --random-order -n auto --dist worksteal --cov=teaagent --cov-context=test --cov-report=term-missing --cov-fail-under=75
+        run: pytest --random-order -n auto --dist worksteal --cov=teaagent --cov-report=term-missing --cov-fail-under=75
 
   test-telemetry:
     runs-on: ubuntu-latest

pyproject.toml

@@ -236,9 +236,6 @@ targets = ["."]
 
 [tool.coverage.run]
 source = ["teaagent"]
-# Per-test context reduces memory pressure from coverage tracking
-# across 5000+ tests under pydantic-core instrumentation.
-context = "test"
 omit = [
     "teaagent/tui/*",
     "teaagent/tournament/*",

teaagent/coordination/signed_approval.py

@@ -5,16 +5,17 @@
 import base64
 import json
 from dataclasses import dataclass
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 try:
     from cryptography.hazmat.primitives.asymmetric.ed25519 import (
         Ed25519PrivateKey,
         Ed25519PublicKey,
     )
 except ImportError:  # pragma: no cover - optional dependency path
-    Ed25519PrivateKey = None  # type: ignore[misc, assignment]
-    Ed25519PublicKey = None  # type: ignore[misc, assignment]
+    if not TYPE_CHECKING:
+        Ed25519PrivateKey = None
+        Ed25519PublicKey = None
 
 
 @dataclass(frozen=True)