fix: pr-bug-scan findings from #1429

[buf0-bot]

Automated fix-PR from pr-bug-scan for parent #1429.

Fixer summary: Narrowed App.tsx theme useEffect dependency from full settings object to settings?.theme so unrelated settings mutations no longer re-run applyDocumentTheme and kill in-progress UI transitions.
Typecheck: skipped

Findings addressed

• ✅ [medium] src/renderer/src/App.tsx:500-518 — Theme effect re-runs on every settings change, briefly killing all transitions

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This PR was generated by the pr-bug-scan automation and reviewed by an agent reviewer. Human approval required before merge.

[nwparker]

Closing — stale-main silent-revert risk.

This PR was branched off the merge of parent #1429 (commit f0de1437) and reports +1/−1 on GitHub, but git diff origin/main..pr-1463 shows it would silently revert at least five PRs that have landed since:

• Make projects the default workspace grouping #1513 — getDefaultUIState is removed and the defaults inlined back into App.tsx.
• fix(terminal): close SIGKILL race for #217 + preserve scrollback on worktree sleep #1454 — the buffer-capture teardown import is reverted from the dedicated shutdown-buffer-captures module back to TerminalPane, and the iteration changes from .values() to a bare iterable.
• fix: focus the right pane after clicking an agent #1451 — activateTabAndFocusPane import is dropped and the inline requestAnimationFrame + FOCUS_TERMINAL_PANE_EVENT dispatch is restored.
• refactor(shortcuts): remove Cmd-hold number-badge hint UI #1412 — dispatchClearModifierHints calls are re-added throughout the keydown handler; refactor(shortcuts): remove Cmd-hold number-badge hint UI #1412 deliberately removed the Cmd-hold number-badge hint UI.
• fix(layout): align right sidebar to top in non-workspace views #1356 — workspace-vs-titlebar layout is restructured (titlebar pulled back outside the left+center wrapper, header heights flipped 36px↔42px, !rightSidebarOpen gating on the toggle removed).

The actual intended fix — narrowing the theme useEffect dep from [settings] to [settings?.theme] — is a one-line change. If the regression is still present on current main, please regenerate the fix from a fresh main checkout so it lands as a clean +1/−1 diff. Not landing via --admin squash because that would erase the five PRs above.