feat(opencode): sync all providers to live config on directory change

Add additive mode support for OpenCode in sync_current_to_live:
- Add AppType::is_additive_mode() to distinguish switch vs additive mode
- Add AppType::all() iterator to avoid hardcoding app lists
- Add sync_all_providers_to_live() for additive mode apps
- Refactor sync_current_to_live to handle both modes

Frontend changes (directory settings):
- Track opencodeDirChanged in useDirectorySettings
- Trigger syncCurrentProvidersLiveSafe when OpenCode dir changes
- Add i18n strings for OpenCode directory settings

src/components/settings/DirectorySettings.tsx

@@ -15,6 +15,7 @@ interface DirectorySettingsProps {
   claudeDir?: string;
   codexDir?: string;
   geminiDir?: string;
+  opencodeDir?: string;
   onDirectoryChange: (app: AppId, value?: string) => void;
   onBrowseDirectory: (app: AppId) => Promise<void>;
   onResetDirectory: (app: AppId) => Promise<void>;
@@ -29,6 +30,7 @@ export function DirectorySettings({
   claudeDir,
   codexDir,
   geminiDir,
+  opencodeDir,
   onDirectoryChange,
   onBrowseDirectory,
   onResetDirectory,
@@ -117,6 +119,17 @@ export function DirectorySettings({
           onBrowse={() => onBrowseDirectory("gemini")}
           onReset={() => onResetDirectory("gemini")}
         />
+
+        <DirectoryInput
+          label={t("settings.opencodeConfigDir")}
+          description={undefined}
+          value={opencodeDir}
+          resolvedValue={resolvedDirs.opencode}
+          placeholder={t("settings.browsePlaceholderOpencode")}
+          onChange={(val) => onDirectoryChange("opencode", val)}
+          onBrowse={() => onBrowseDirectory("opencode")}
+          onReset={() => onResetDirectory("opencode")}
+        />
       </section>
     </>
   );

src/components/settings/SettingsPage.tsx

@@ -307,6 +307,7 @@ export function SettingsPage({
                           claudeDir={settings.claudeConfigDir}
                           codexDir={settings.codexConfigDir}
                           geminiDir={settings.geminiConfigDir}
+                          opencodeDir={settings.opencodeConfigDir}
                           onDirectoryChange={updateDirectory}
                           onBrowseDirectory={browseDirectory}
                           onResetDirectory={resetDirectory}