Isolate docs eval tools and retain final evidence

[nicholasdbrady]

Summary

• expose only each selected MCP server's exact fully qualified documentation tools; retain deferTools: "never", one config, built-in MCP disablement, and server permission
• enforce exact configured tool membership in runner, scorer, and Azure proof
• retain bounded post-result metadata: line/type/ephemeral plus structured server states containing canonical name/status, every supplied identity/status alias, exact error-field names/presence, total counts, truncation, and shape validity
• mcp.tools.list_changed requires exactly the selected server identity, no status, no error/failure fields, and ephemeral=true
• status changes allow only selected connected/ready or builtin github-mcp-server disabled, with consistent aliases and no error fields
• loaded summaries require every entry named and typed, selected server present, no foreign/duplicate/error entries, and each entry exactly selected connected/ready or builtin disabled
• reject conflicting identity/status aliases and alias arrays beyond runner-representable cardinality; scorer independently enforces all lifecycle rules
• fail closed on semantic, unknown, non-ephemeral, failing lifecycle, duplicate-result, or truncated post-result evidence
• compute Azure selected-search proof before other validity short circuits and retain it on invalid/timeout rows without changing row validity

Artifact 8755138625 cannot reveal prior exact post-result types because all affected excerpts truncate before the result; this PR closes that gap conservatively.

Validation

• python -m pytest tests\test_docs_eval_evidence.py -q — 322 passed, 2 POSIX-specific tests skipped on Windows
• python -m ruff check scripts\run_docs_eval.py scripts\eval_scorer.py tests\test_docs_eval_evidence.py — passed
• runner/scorer tests cover allowed selected/builtin cases and foreign, unnamed, duplicate, error-bearing, shape-invalid, alias-conflicting, and oversized-alias cases
• exact selected-tool isolation and Azure invalid/timeout proof tests retained

Do not merge or rerun the full matrix until reviewed.