test: add comprehensive E2E tests for MCP server (#39)

* test: add comprehensive E2E tests for MCP server

Add test_server_e2e.py with full coverage of all 26 MCP tools:

Session Management:
- list_sessions, get_session, create_session, create_session_from_template
- delete_session, restart_session, clone_session, update_session

Observability:
- get_session_logs, get_session_transcript, get_session_metrics

Labels:
- label_resource, unlabel_resource, list_sessions_by_label
- bulk_label_resources, bulk_unlabel_resources

Bulk Operations:
- bulk_delete_sessions, bulk_stop_sessions, bulk_restart_sessions
- bulk_delete_sessions_by_label, bulk_stop_sessions_by_label
- bulk_restart_sessions_by_label

Cluster Management:
- list_clusters, whoami, switch_cluster, login

Test Infrastructure:
- MockHTTPClient class with response matching and call verification
- make_response helper for creating mock httpx responses
- Fixtures for cluster config, settings, and HTTP client

Test Coverage Includes:
- Success and error path testing
- Dry-run mode verification
- Confirmation requirement enforcement for destructive operations
- Input validation testing (invalid project, template, etc.)
- Complete session lifecycle workflow simulation
- Edge cases (empty lists, no matches, partial failures)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(ci): apply ruff formatting to test_server_e2e.py

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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Co-authored-by: Ambient Code Bot <bot@ambient-code.local>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: 3 people