Document editor: Milkdown (Crepe) + agent-aware features (retrieval preview, [[memory-link]])

[ajianaz]

Requires uteke: v0.16.0+ · Epic: #289

What

• Replace docs textarea with Milkdown Crepe (markdown-native; BlockNote is React-only — corrected decision) wrapped for Svelte 5 (action + teardown; no per-keystroke framework churn).
• Write flow: slash menu, block drag handle, markdown shortcuts, paste-markdown → blocks, code blocks with language picker + copy button, ⌘S + 2.5s debounced autosave + Saved indicator, unsaved guard.
• Conflict detection: compare updatedAt before POST /doc/update; if changed externally → dialog (compare / overwrite). Local snapshots (IndexedDB, last 20) for emergency restore.
• Retrieval Preview panel: test query → /doc/search shows rank + snippet for this doc ("will the agent find this?").
• [[memory-link]]: [[ triggers /recall suggestions; inserts markdown link [title](uteke://memory/<id>) (plain markdown — agents read it via /doc/get without adapters).
• v1 cuts (explicit): image upload (external URLs only — uteke has no blob storage), comments, collaboration, advanced table editing.

Why

Human-writes→agent-reads is the product bridge; markdown-native state = zero serialization drift between what the human sees and what the agent reads (P37). Retrieval preview answers the #1 writing anxiety at the moment of hesitation (P14).

Testing

• Unit: markdown round-trip (parse→serialize == source on fixtures), conflict path, snapshot restore.
• E2E: type/paste/save/reopen fidelity; [[link]] insert; retrieval preview returns result.
• Visual QA: editor in both themes; statusbar states (dirty/saved/conflict).