feat: add is_subagent flag to agents, fix all lint/type/test issues

- Add is_subagent checkbox to agent editor; subagents are hidden from Chat Settings
- Add is_subagent field to AgentDefinition type, TOML serialization, and API route
- Filter subagents from ModelSelector agent list
- Fix all biome lint/format errors across codebase (useLiteralKeys, noNonNullAssertion, noExplicitAny, formatting, import sorting)
- Fix svelte-check errors (type narrowing in SkillsBrowser, ToolPermissions, SidebarPanel)
- Fix a11y warnings in App.svelte (label-control associations)
- Fix test mocks missing BackgroundShellStore, BackgroundTranscriptStore, createWebSearchTool, createYoutubeTranscribeTool
- Update stale 409 test to match current message-queuing behavior
- Exclude packaging/ and release/ dirs from biome to avoid linting stale build artifacts

1 files changed, 1 insertions, 3 deletions

diff --git a/packages/frontend/src/lib/components/ModelStatus.svelte b/packages/frontend/src/lib/components/ModelStatus.svelte
index d6ff0f5..57c5efd 100644
--- a/packages/frontend/src/lib/components/ModelStatus.svelte
+++ b/packages/frontend/src/lib/components/ModelStatus.svelte
@@ -48,8 +48,6 @@ let keyModalError = $state<string | null>(null);
 let keyModalSaving = $state(false);
 let removingKey = $state<string | null>(null);
 
-
-
 async function loadCredentialStatus(): Promise<void> {
 	try {
 		const res = await fetch(`${apiBase}/models/credentials-status`);
@@ -173,7 +171,7 @@ function timeAgo(ts: number | null): string {
 
 function truncate(str: string | null, max: number): string {
 	if (!str) return "";
-	return str.length > max ? str.slice(0, max) + "..." : str;
+	return str.length > max ? `${str.slice(0, max)}...` : str;
 }
 </script>