fix(graph): keep the focused node highlighted across tab switches

[hamidfzm]

Summary

Clicking a node in the graph highlights it and its neighbourhood. Switching to another tab and back dropped that highlight, because the graph tab unmounts while inactive and the focused node lived only in component state. The camera and layout already survive the switch (#732); this keeps the focused node with them. Follow-up to #733.

Changes

• graphViewStore: add focusedId to the per-workspace graph view state.
• useGraphFocus: take an optional persistKey, seed the focused node from the store on mount and write it back when it changes.
• GraphView: pass the workspace root as persistKey.
• Test: focus a node, unmount, remount in the same workspace, and the neighbourhood is still highlighted.

Risk classification

• Persistence / data loss
• Asynchronous ordering / races
• Destructive lifecycle (close, unmount, workspace switch, app exit)
• Filesystem / IPC surface
• Untrusted rendering (Markdown, plugins, links)
• Secrets / credentials
• Network
• Migrations / persisted-format changes
• Accessibility
• Bundle size / startup
• No risk areas touched

Invariants at stake and evidence

Session-only, in-memory state; nothing reaches disk. The focus rides the existing store lifecycle:

• Unmount on tab switch: focus restored, covered by GraphView.test.tsx "comes back with the focused node still highlighted" (verified to fail without the fix).
• Closing the graph tab: pruneGraphViews drops the whole entry, so a reopened graph starts unfocused.
• A focused note deleted or renamed while the tab is inactive: the existing stale-id check in useGraphFocus clears it on the next mount.
• Workspaces stay isolated: the store is keyed by workspace root.
• Pending camera move: still cancelled on unmount, so only the highlight is restored.

Testing

Automated gates only: pnpm typecheck, pnpm check, full pnpm test (3953 tests). No Rust changes. Not yet checked by hand in the running app.

• Tested on macOS
• Tested on Windows
• Tested on Linux

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.69%. Comparing base (b15f37a) to head (d8e0cd1).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #764   +/-   ##
=======================================
  Coverage   99.69%   99.69%           
=======================================
  Files         548      548           
  Lines       22587    22590    +3     
  Branches     2467     2468    +1     
=======================================
+ Hits        22519    22522    +3     
  Misses         17       17           
  Partials       51       51           

Flag	Coverage Δ
frontend	99.41% <100.00%> (+<0.01%)	⬆️
rust	99.92% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/components/graph/GraphView.tsx	100.00% <ø> (ø)
src/hooks/useGraphFocus.ts	100.00% <100.00%> (ø)
src/lib/graphViewStore.ts	100.00% <ø> (ø)

[codecov]

Bundle Report

Changes will increase total bundle size by 111 bytes (0.0%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
glyph-frontend-esm	19.18MB	111 bytes (0.0%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: glyph-frontend-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
assets/GraphView-*.js	111 bytes	23.37kB	0.48%

Files in assets/GraphView-*.js:

• ./src/components/graph/GraphView.tsx → Total Size: 5.31kB

• ./src/hooks/useGraphFocus.ts → Total Size: 2.06kB