[Harry19081]

Problem

Station and chat header rows reserve an inset under the window's pinned chrome. #1838 made that inset animate only while a station opens or closes (useStationToggleInsetTransition), so tab changes stopped gliding the header controls. The sidebar collapse and the chat pane opening or closing also move a pane on PANE_WIDTH_TRANSITION_CLASSES and change the same reservation. For those toggles the inset still snapped: the header content jumped by the whole reservation on the first frame, then glided along with the pane, landing somewhere it never travelled to.

Solution

• usePaneLayoutInsetTransition (in src/scaffold/AppLayout) replaces useStationToggleInsetTransition. It watches a layout signature made of three flags: station open (effectiveChatPanelMaximizedAtom), sidebar collapsed (sidebarCollapsedAtom), and chat pane open (chatWidthAtom > 0).
• When the signature changes, the hook returns CHROME_INSET_TRANSITION_CLASSES for 320 ms. The class is added in the same render as the new inset, and each change ends only its own timer.
• Anything that changes a reservation without moving a pane still snaps: tab, session, station or route switches, and dragging the chat divider (only crossing zero width flips the chat flag).
• Callers are swapped one for one: ChatPanelHeader, the My Station TabBar, and AgentStationTopHeader. The CHROME_INSET_TRANSITION_CLASSES doc comment is updated to match.

Potential risks

• This widens the rule settled in fix(station-chrome): animate header insets only on station toggle #1838 ("insets animate only on station open/close") to all three pane toggles. Reviewers should confirm that is still the intended design.
• Closing the chat pane by dragging the divider to zero flips the chat flag, so that one moment gets a 320 ms inset transition.
• Not checked in the running app: the Tauri app could not be captured from this environment, so there are no recordings of the motion.

Verification

• pnpm exec vitest run --config config/vitest.config.ts src/scaffold/AppLayout src/engines/ChatPanel/__tests__ src/engines/ChatPanel/ChatPanelHeader src/modules/WorkStation/shared/TabBar src/scaffold/WorkbenchChrome src/components/layout: 168 passed.
  • The new usePaneLayoutInsetTransition.test.ts covers: at rest; sidebar, chat pane and station toggles; tab re-renders; overlapping changes; divider drags.
  • The old hook's test is removed with the hook.
• npx tsgo --noEmit: exit 0. No remaining references to useStationToggleInsetTransition under src/ or tests/.
• pnpm exec prettier --check and pnpm exec eslint --max-warnings 0 --report-unused-disable-directives on the changed files: clean.
• The pre-commit hook ran on the commit (lint-staged with oxlint, eslint and prettier, plus tsgo gated to staged files). The commit has no Pre-commit hook ran. trailer because it was made in a linked worktree, where .git is a file and the stats step cannot write its output.
• Not run: the full vitest suite and E2E.