fix(ingestion): support live WAL and JSON Canvas materials

[DTALEX66]

Scope

• Add safe native JSON Canvas parsing for text/file/link/group nodes without opening attachments, following links, requesting URLs, or executing node content.
• Allow internal Knowledge/Research/Learning runtime reads against query-only live-WAL databases while preserving checkpoint-only fail-closed behavior for offline read-only consumers.
• Add regression coverage for Canvas detection/projection and Research approval from a live-WAL database.
• Add the locked markitdown CI dependency used by the existing multi-format adapter surface.

Verification

• Targeted local regression: 19 passed in 1.08s.
• Full material intake: 1161/1161 HTTP 200; 1140 Markdown, 20 Canvas, 1 TXT.
• Durable jobs: 1072 succeeded; idempotent job count is lower than file count because source/content records coalesce.
• Durable delivery: 1072 delivered, 1072 receipts recorded, 0 pending, 0 missing.
• Restart readback: health 200 and all durable counts unchanged.
• Browser failure/retry/replay matrix: BROWSER_FAILURE_RETRY_REPLAY_PASS.

Boundaries

• No canonical user WIP was staged or modified.
• No source material directory or E: path was written or accessed.
• No Hermes global state was modified.
• No Release or immutable tag was changed.

Risk and rollback

The live-WAL mode is opt-in for internal runtime paths and keeps PRAGMA query_only=ON; offline/checkpoint-only callers retain the existing sidecar refusal. Roll back by reverting commit 36ce710.

CI

PR-head exact-SHA CI is required before merge. Merge-SHA main CI and any release qualification are not yet executed for this candidate.