fix(dashboard): activity filter auto-expand, jargon cleanup, autopilot stop UX

[hopeatina]

Summary

• Time filter auto-expand fix: "Last hour" (and other filters) no longer silently auto-expand when the list is short. Auto-expand now requires the user to have scrolled, and has a 3-second cooldown after manual filter changes.
• Jargon cleanup: Replaced developer-facing text in activity timeline — "requested dispatch" → "requested a run", → arrow notation → "handed off to", "sync replay events" → "background sync events", and rewrote the Filters menu description.
• Autopilot stop UX: Button now shows "Stopping Autopilot…" and stays disabled while the run is gracefully stopping, instead of re-enabling as "Stop Autopilot" which made users think the stop didn't work.

Test plan

• npm run build — builds pass (verified)
• cd dashboard && npx tsc --noEmit — zero type errors (verified)
• Select "Last hour" → scroll to bottom → filter should NOT auto-expand to "Today" unless user actively scrolls
• After 3+ seconds of user scroll past all items, auto-expand triggers normally
• Activity cards show "requested a run" instead of "requested dispatch"
• Handoff cards show "X handed off to Y" instead of "X -> Y"
• Filters menu shows "background sync events" (not "sync replay events")
• Click "Stop Autopilot" → button shows "Stopping Autopilot…" and stays disabled until run stops

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