feat: combine session actions into options dropdown

SessionCard desktop view:
- Retain primary action button: Open (active) or Start (inactive)
- Replace individual Stop/Tunnel/Delete buttons with a single Options
  dropdown triggered by a ⋯ button
- Dropdown contains applicable actions:
  - Active: Stop, Recreate Tunnel (web), Delete
  - Inactive: Start, Delete
- Add window.confirm before Delete as a safety net
- Dropdown closes on outside click or Escape key
- Add 'more' icon (DotsThreeVertical) to icon component
- Add session-options-dropdown CSS with subtle animation

Mobile view unchanged (already uses MobileActionSheet).

Quality gates: tsc --noEmit pass, npm run build pass, 82/82 tests pass

apps/web/src/components/icon.tsx

@@ -35,6 +35,7 @@ import {
 	Terminal,
 	ArrowLeft,
 	DotsSixVertical,
+	DotsThreeVertical,
 	Bell,
 	CaretDown,
 	CaretRight,
@@ -81,6 +82,7 @@ export type IconName =
 	| "terminal"
 	| "arrow-left"
 	| "drag"
+	| "more"
 	| "bell"
 	| "chevron-down"
 	| "chevron-right";
@@ -132,6 +134,7 @@ const iconMap: Record<
 	terminal: Terminal,
 	"arrow-left": ArrowLeft,
 	drag: DotsSixVertical,
+	more: DotsThreeVertical,
 	bell: Bell,
 	"chevron-down": CaretDown,
 	"chevron-right": CaretRight,