feat(ci): accelerate devops ci performance with worker auto-scaling, test hotspot isolation, and zero-blocking dispatch

[dan-petty]

Problem Statement

devops ci currently takes ~3m 15s to complete. Profiling revealed three primary bottlenecks:

1. Hardcoded --maxprocesses=4 throttling pytest xdist workers, leaving up to 75% of available CPU cores idle on multi-core systems.
2. Pathological unit tests with unmocked socket/network probes and unbounded workspace directory traversal (test_k8s_bootstrap_success taking 78s, test_repomap_cli taking 70s, test_ci.py taking 46s), consuming over 250s of CPU time.
3. Synchronous sequential execution of docs_fix (DocGenerator.check_docs) running for 16.5s before background concurrent tasks (including pytest) are launched.

Acceptance Criteria

1. Dynamically scale pytest xdist workers based on available CPU cores (min(os.cpu_count() or 4, 16)), removing the hardcoded --maxprocesses=4 limit.
2. Isolate test hotspots with proper mocking:
   • Mock devops_cli.commands.k8s.networking.configure_urls in tests/test_k8s_context.py (dropping from 78s to <0.05s).
   • Pass isolated tmp_path target in tests/test_ai_repomap.py (dropping from 70s to <0.1s).
   • Mock workspace fingerprinting in tests/test_ci.py (dropping from 46s to <0.05s).
3. Reorder pipeline dispatch so that pytest is launched immediately without waiting for synchronous docs checks.
4. Maintain 100% test pass rate, code coverage >= 90%, and strict complexity M <= 10.

[dan-petty]

Closed via PR #261.