Use @extrachill/chat canonical diff parser, delete local fork

[chubes4]

Summary

The editor carried a parallel src/diff/canonicalDiff.ts with its own CanonicalDiffType / CanonicalDiffStatus / CanonicalDiffItem / CanonicalDiffData types and its own parseCanonicalDiffFromJson. That duplication existed because the upstream parser only recognized container.diff as a nesting layer, while Data Machine's unified PendingActionHelper::stage() envelope nests the preview payload under container.preview.

@extrachill/chat@0.11.0 (just published) lands three relevant changes:

• chat #21 — adds actionId as the canonical field on CanonicalDiffData (alongside a deprecated diffId alias). The editor already spoke actionId so no vocabulary change was needed here, but the type on the upstream package was missing it until 0.11.
• chat #22 — forwards onToolCalls + sessionContext from <Chat> to useChat. Not used by this file directly, but relevant for other editor work.
• chat #23 — parseCanonicalDiff now recognizes container.preview and container.preview_data as nesting keys. That's exactly the shape our local fork existed to handle.

With 0.11 in place, the local fork is redundant.

Migration

• src/types.ts — import CanonicalDiffData / CanonicalDiffType from @extrachill/chat instead of ./diff/canonicalDiff.
• src/sidebar/EditorChatSidebar.tsx — add parseCanonicalDiffFromJson to the existing @extrachill/chat imports, drop the local import.
• Delete src/diff/canonicalDiff.ts (92 lines).
• Bump @extrachill/chat from ^0.10.1 to ^0.11.0 in package.json.

Behaviour

No runtime change. The upstream parser now handles the same nesting shapes our fork did, and we were already consuming the actionId field which v0.11 surfaces on the typed shape.

Validation

• npm install @extrachill/chat@^0.11.0 — resolves to 0.11.0 from the npm registry.
• npm run typecheck — clean.
• npm run build — clean.

Diff stat

 package-lock.json                 |  8 ++--
 package.json                      |  2 +-
 src/diff/canonicalDiff.ts         | 92 ---------------------------------------
 src/sidebar/EditorChatSidebar.tsx |  2 +-
 src/types.ts                      |  2 +-
 5 files changed, 7 insertions(+), 99 deletions(-)

AI assistance

• AI assistance: Yes
• Tool(s): Claude Code (Opus 4.7)
• Used for: Identified the parallel-parser duplication during the cross-repo chat audit, drafted the upstream chat changes (#21/#22/#23) to eliminate the divergence, then cut 0.11 and migrated this consumer. Chris flagged the editor alignment and cut the release.