Escape key doesn't dismiss run views (pre-run, checkpoint, run history)

[MatthewLones]

Description

Pressing the Escape key does nothing in three views that should support keyboard dismissal:

View	Component	Type	Existing close mechanism
New Run	PreRunPanel	dockview panel	"Cancel" button → closeTab('pre-run')
Checkpoint	CheckpointPage	route (/runs/:id/checkpoint)	"Back to Run" button → navigate()
Run History	RunHistoryPanel	dockview panel	Tab close only (no button)

Root Cause

None of these components register keyboard event listeners. The global Escape handler in WorkspacePage.tsx:237-244 only dismisses the settings overlay.

Fix Required

1. PreRunPanel + RunHistoryPanel (dockview panels): Extend the global Escape handler in WorkspacePage.tsx to close the active dockview panel when Escape is pressed
2. CheckpointPage (route): Add a useEffect with a keydown listener that calls navigate(-1) on Escape

Files Involved

• packages/ui/src/pages/WorkspacePage.tsx — extend Escape binding (~line 237)
• packages/ui/src/pages/CheckpointPage.tsx — add keydown listener
• packages/ui/src/pages/RunDashboardPage.tsx — Escape for run history if viewed from dashboard