feat: version history for sketches (image documents) (#4719)

* feat: sketch document version history — data layer

Mirror timeline sequence versioning (#4712) for sketches: an
image_document_versions table with a per-document monotonic version
number, an ImageDocumentVersion model (snapshot with unique-violation
retry, autosave pruning that never touches manual/restore snapshots),
the migration plus PG bootstrap DDL, and the protocol schemas for the
document-level version history distinct from per-layer generation takes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018yzrorMvguPf5DMZjMRNP8

* feat: sketch document version history — router, CLI, harness

The sketch tRPC router gains a documentVersions sub-router (list, get,
create, restore, delete) alongside the existing per-layer generation
takes: restore snapshots the pre-restore state first so it is undoable,
sketch.update writes a best-effort autosave at most every five minutes
(20 kept, pruned), and sketch.delete removes the document's history.

nodetool sketch versions list|show|create|restore|delete reads and
writes the same history against the local database; restore CAS-writes
the snapshot back and exits non-zero when the restored document no
longer parses as a JSON object. The sketch surface and its harness are
registered in the harness registry, and CLAUDE.md documents the command.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018yzrorMvguPf5DMZjMRNP8

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: georgi

CLAUDE.md

@@ -667,6 +667,30 @@ old document is restored against today's schema, so what it used to pass is not
 what it passes now — a restore whose document no longer validates exits
 non-zero and prints the issues.
 
+### nodetool sketch versions (Sketch Version History)
+
+`sketch versions` reads and writes an image document's snapshot history against
+the local database — manual saves, the autosaves `sketch.update` writes at most
+every five minutes, and the pre-restore snapshot that makes a restore undoable.
+The per-layer generation takes (`sketch.versions.*` in the tRPC router) are a
+different thing: those record one generated image on one layer, these snapshot
+the whole document. All five subcommands take `--json`.
+
+```bash
+npm run dev:nodetool -- sketch versions list <image_document_id> --save-type manual --limit 10
+npm run dev:nodetool -- sketch versions show <image_document_id> 3 --json
+npm run dev:nodetool -- sketch versions create <image_document_id> --name "before the repaint"
+npm run dev:nodetool -- sketch versions restore <image_document_id> 3
+npm run dev:nodetool -- sketch versions delete <image_document_id> 3 --yes
+```
+
+`restore` mirrors the tRPC router (`sketch.documentVersions.restore`): it
+snapshots the current state as a `restore` version, then CAS-writes the old
+document and its canvas settings back onto the image document. A sketch has no
+validator harness, so the check afterwards is the one a headless run can make —
+the restored document must still parse as a JSON object; one that no longer
+does exits non-zero. Layer bitmaps stay opaque to that check.
+
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