feat(overlay): add primary subtitle bar visibility modes (#63)

- Cycle `v` through `hidden | visible | hover` instead of a boolean toggle
- Add `subtitleStyle.primaryDefaultMode` config with default `visible`
- Carry primary mode independently from secondary in hot-reload payload
- Add hover CSS: transparent until hovered, then fully visible
- Show primary-specific OSD text on each mode change

src/main/runtime/config-hot-reload-handlers.test.ts

@@ -2,6 +2,7 @@ import test from 'node:test';
 import assert from 'node:assert/strict';
 import { DEFAULT_CONFIG, deepCloneConfig } from '../../config';
 import {
+  buildConfigHotReloadPayload,
   buildRestartRequiredConfigMessage,
   createConfigHotReloadAppliedHandler,
   createConfigHotReloadMessageHandler,
@@ -56,6 +57,17 @@ test('createConfigHotReloadAppliedHandler runs all hot-reload effects', () => {
   );
 });
 
+test('buildConfigHotReloadPayload includes independent primary subtitle mode', () => {
+  const config = deepCloneConfig(DEFAULT_CONFIG);
+  config.subtitleStyle.primaryDefaultMode = 'hover';
+  config.secondarySub.defaultMode = 'hidden';
+
+  const payload = buildConfigHotReloadPayload(config);
+
+  assert.equal(payload.primarySubMode, 'hover');
+  assert.equal(payload.secondarySubMode, 'hidden');
+});
+
 test('createConfigHotReloadAppliedHandler skips optional effects when no hot fields', () => {
   const config = deepCloneConfig(DEFAULT_CONFIG);
   const calls: string[] = [];

src/main/runtime/config-hot-reload-handlers.ts

@@ -54,6 +54,7 @@ export function buildConfigHotReloadPayload(config: ResolvedConfig): ConfigHotRe
     sessionBindingWarnings,
     subtitleStyle: resolveSubtitleStyleForRenderer(config),
     subtitleSidebar: config.subtitleSidebar,
+    primarySubMode: config.subtitleStyle.primaryDefaultMode,
     secondarySubMode: config.secondarySub.defaultMode,
   };
 }