Add UX rework design doc

Covers three changes: skip move-only autosaves, add detailed diff
metadata for hover tooltips, and hide branching UI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/plans/2026-04-03-ux-rework-design.md

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+# UX Rework Design — 2026-04-03
+
+## Context
+
+After regular use, three pain points emerged:
+1. Autosave generates too many snapshots (moves spam the timeline bar)
+2. Branching UI is confusing and never used
+3. No way to know what specifically changed when hovering a snapshot
+
+## Changes
+
+### 1. Autosave — Skip move-only snapshots
+
+**Problem:** Moving nodes triggers auto-captures as frequently as structural changes, filling the timeline fast.
+
+**Solution:** Add a guard in the capture path: if `detectChangeType()` returns `'move'`, skip the save and return early. No new config, no debounce changes.
+
+Existing snapshots are unaffected.
+
+### 2. Detailed diff metadata on hover
+
+**Problem:** Snapshot icons show a change type icon but not *what* specifically changed.
+
+**Solution:** At capture time, after `detectChangeType()`, run a new `computeDetailedDiff(prevGraph, currentGraph)` that produces:
+
+```json
+{
+  "added": ["CLIPTextEncode", "KSampler"],
+  "removed": ["VAEDecode"],
+  "params": ["KSampler: steps 20→30", "KSampler: cfg 7→9"]
+}
+```
+
+This object is stored in snapshot metadata. On hover in the sidebar or timeline, a tooltip renders these lines as plain text.
+
+For snapshots captured before this change (no `diff` field), the tooltip falls back to the existing change type label.
+
+**Diff computation:**
+- Added/removed nodes: compare node sets by ID, label by title+type
+- Changed params: compare `widgets_values` per node between previous and current graph
+
+### 3. Hide branching UI
+
+**Problem:** Branch navigation is confusing and adds visual noise.
+
+**Solution:** Add `const BRANCHING_ENABLED = false` at the top of `snapshot_manager.js`. All branch UI rendering (the `< 1/2 >` navigator, branch buttons, `activeBranchSelections` sidebar/timeline logic) checks this flag and skips when false.
+
+Underlying data and code (parentId, buildSnapshotTree, etc.) are left intact.
+
+## Out of Scope
+
+- Removing branching code
+- Making branching a user-facing settings toggle
+- Changing debounce timing
+- Retroactively hiding or deleting move-type snapshots