fix: persist runtime probe evidence

[Q00]

Summary

• fixes feat(auto): runtime-probe envelope + advisory probe_runner (L3-2) #1190 runtime probe durability by persisting runtime_probe_evidence into AutoPipelineState
• preserves persisted probe evidence when completed sessions are replayed/resumed
• adds an opt-in public CLI/MCP runtime probe runner via OUROBOROS_RUNTIME_PROBE_COMMAND for PRODUCT_COMPLETE validation

Verification

• uv run ruff check src/ouroboros/auto/pipeline.py src/ouroboros/auto/state.py src/ouroboros/auto/adapters.py src/ouroboros/orchestrator/runtime_evidence.py src/ouroboros/cli/commands/auto.py src/ouroboros/mcp/tools/auto_handler.py tests/unit/auto/test_pipeline_runtime_probe_envelope.py
• uv run pytest tests/unit/auto/test_pipeline_runtime_probe_envelope.py tests/unit/orchestrator/test_runtime_evidence.py -q

[shaun0927]

Cross-checked against #1190 (the L3-2 envelope + probe_runner contract) and #1181 (RuntimeEvidence substrate). Three things I verified:

1. Persistence scope is correct — state.runtime_probe_evidence is per-session, hydrated at the start of run() and replaces the explicit self._last_probe_evidence = () clear. This is not a "leak across AutoPipeline instances" regression because a fresh AutoPipelineState still starts with runtime_probe_evidence=[]; the persistence only kicks in for resume/re-attach of the same logical session, which is exactly the gap #1190 acknowledged ("caches evidence... in the same run").
2. EnvRuntimeProbeRunner is strictly opt-in — returns () when OUROBOROS_RUNTIME_PROBE_COMMAND is unset, so wiring it whenever complete_product=True is behaviorally identical to the previous probe_runner=None default for any caller that doesn't set the env var. Aligns with #1190's "the caller decides".
3. RuntimeEvidence.to_dict/from_dict round-trip is safe — explicit type validation for each field, _json_safe_payload handles non-JSON-safe values via default=str fallback, and _validate_loaded rejects malformed entries. from_dict defaulting payload.setdefault("runtime_probe_evidence", []) covers older state files cleanly.

No conflicts with the other open auto PRs since this touches auto/{pipeline,state,adapters}.py, mcp/tools/auto_handler.py, and orchestrator/runtime_evidence.py in additive places — verified against #1196 / #1194 line ranges. Safe to merge.