fix(tests): resolve CI test failures — pool auto-seeding, stale assertions, mock isolation

Salvaged from PR #10643 by kshitijk4poor, updated for current main.

Root causes fixed:
1. Telegram xdist mock pollution — new tests/gateway/conftest.py with shared
   mock that runs at collection time (prevents ChatType=None caching)
2. VIRTUAL_ENV env var leak — monkeypatch.delenv in _detect_venv_dir tests
3. Copilot base_url missing — add fallback in _resolve_runtime_from_pool_entry
4. Stale vision model assertion — zai now uses glm-5v-turbo
5. Reasoning item id intentionally stripped — assert 'id' not in (store=False)
6. Context length warning unreachable — pass base_url to AIAgent in test
7. Kimi provider label updated — 'Kimi / Kimi Coding Plan' matches models.py
8. Google Workspace calendar tests — rewritten for current production code,
   properly mock subprocess on api_module, removed stale +agenda assertions
9. Credential pool auto-seeding — mock _select_pool_entry / _resolve_auto /
   _import_codex_cli_tokens to prevent real credentials from leaking into tests

tests/run_agent/test_invalid_context_length_warning.py

@@ -9,6 +9,8 @@ def _build_agent(model_cfg, custom_providers=None, model="anthropic/claude-opus-
     if custom_providers is not None:
         cfg["custom_providers"] = custom_providers
 
+    base_url = model_cfg.get("base_url", "")
+
     with (
         patch("hermes_cli.config.load_config", return_value=cfg),
         patch("agent.model_metadata.get_model_context_length", return_value=128_000),
@@ -21,6 +23,7 @@ def _build_agent(model_cfg, custom_providers=None, model="anthropic/claude-opus-
         agent = AIAgent(
             model=model,
             api_key="test-key-1234567890",
+            base_url=base_url,
             quiet_mode=True,
             skip_context_files=True,
             skip_memory=True,