feat(notifications): add notification history panel and overlay UX fixes

- New toggleNotificationHistory (Ctrl+N) session-scoped history panel; slides in from same edge as notification stack
- Overlay error/recovery toast follows notifications.overlayPosition; stack and history side seeded at startup
- Cold managed background startup initializes tray and visible overlay shell before tokenization warmups finish
- Add Update button to overlay update-available notifications
- Fix Ctrl+S sentence-card flow: only Anki progress notification, no duplicate status toast
- Fix overlay notification close/actions clickability above subtitle bars on Linux
- Increase pause-until-ready default timeout from 15s to 30s

scripts/test-plugin-start-gate.lua

@@ -1915,6 +1915,32 @@ do
 	)
 end
 
+do
+	local recorded, err = run_plugin_scenario({
+		process_list = "",
+		option_overrides = {
+			binary_path = binary_path,
+			auto_start = "yes",
+			auto_start_visible_overlay = "yes",
+			auto_start_pause_until_ready = "yes",
+			auto_start_pause_until_ready_owns_initial_pause = "yes",
+			socket_path = "/tmp/subminer-socket",
+		},
+		input_ipc_server = "/tmp/subminer-socket",
+		media_title = "Random Movie",
+		paused = true,
+		files = {
+			[binary_path] = true,
+		},
+	})
+	assert_true(recorded ~= nil, "plugin failed to load for default pause timeout scenario: " .. tostring(err))
+	fire_event(recorded, "file-loaded")
+	assert_true(
+		has_timeout(recorded.timeouts, 30),
+		"pause-until-ready default timeout should give cold app startup 30 seconds"
+	)
+end
+
 do
 	local recorded, err = run_plugin_scenario({
 		process_list = "",