headless: export trajectory artifacts from frozen SQLite state

[likun666661]

Summary

• publish a frozen selected-session trajectory-state snapshot after Harbor cell runs that reference image Artifacts
• hydrate trajectories from the standalone SQLite snapshot and only its referenced payloads
• remove trajectory fallback to artifacts/metadata.jsonl and live runtime.sqlite-wal copying
• fail closed on invalid SQLite integrity/schema/cutover state, index/JSON mismatches, and payload size/MIME mismatches

This completes the trajectory/export slice of the SQLite operational-state migration. After this PR, issue #1649 can move to the compatibility-writer removal stage.

Verification

• npm --workspace @maka/storage run build
• full Storage test suite: pass
• npm --workspace @maka/headless run build
• full harbor-cell.test.js: pass
• trajectory builder + Maka adapter hydration contracts: pass
• python3 -m py_compile packages/headless/harbor/maka_agent.py packages/headless/harbor/maka_trajectory.py
• npx biome check on changed TypeScript files
• git diff --check

Local full Headless run: 1427 passed, 5 skipped, and 2 unchanged Python 3.9 CLI smoke failures (kimi_code_agent.py timeout and codex_agent.py event-loop initialization). Neither failing test or implementation is touched by this patch.

Part of #1649