UI: expand-to-canvas, session navigation, plugin SDK fixes (#49483)

* Plugins: fix signal SDK circular re-exports and reserved commands TDZ

* UI: add expand-to-canvas button and in-app session navigation

* changelog: UI expand/navigate and plugin TDZ/import fixes

src/plugins/commands.ts

@@ -35,50 +35,15 @@ let registryLocked = false;
 const MAX_ARGS_LENGTH = 4096;
 
 /**
- * Reserved command names that plugins cannot override.
- * These are built-in commands from commands-registry.data.ts.
+ * Reserved command names that plugins cannot override (built-in commands).
+ *
+ * Constructed lazily inside validateCommandName to avoid TDZ errors: the
+ * bundler can place this module's body after call sites within the same
+ * output chunk, so any module-level const/let would be uninitialized when
+ * first accessed during plugin registration.
  */
-const RESERVED_COMMANDS = new Set([
-  // Core commands
-  "help",
-  "commands",
-  "status",
-  "whoami",
-  "context",
-  "btw",
-  // Session management
-  "stop",
-  "restart",
-  "reset",
-  "new",
-  "compact",
-  // Configuration
-  "config",
-  "debug",
-  "allowlist",
-  "activation",
-  // Agent control
-  "skill",
-  "subagents",
-  "kill",
-  "steer",
-  "tell",
-  "model",
-  "models",
-  "queue",
-  // Messaging
-  "send",
-  // Execution
-  "bash",
-  "exec",
-  // Mode toggles
-  "think",
-  "verbose",
-  "reasoning",
-  "elevated",
-  // Billing
-  "usage",
-]);
+// eslint-disable-next-line no-var -- var avoids TDZ when bundler reorders module bodies in a chunk
+var reservedCommands: Set<string> | undefined;
 
 /**
  * Validate a command name.
@@ -97,8 +62,41 @@ export function validateCommandName(name: string): string | null {
     return "Command name must start with a letter and contain only letters, numbers, hyphens, and underscores";
   }
 
-  // Check reserved commands
-  if (RESERVED_COMMANDS.has(trimmed)) {
+  reservedCommands ??= new Set([
+    "help",
+    "commands",
+    "status",
+    "whoami",
+    "context",
+    "btw",
+    "stop",
+    "restart",
+    "reset",
+    "new",
+    "compact",
+    "config",
+    "debug",
+    "allowlist",
+    "activation",
+    "skill",
+    "subagents",
+    "kill",
+    "steer",
+    "tell",
+    "model",
+    "models",
+    "queue",
+    "send",
+    "bash",
+    "exec",
+    "think",
+    "verbose",
+    "reasoning",
+    "elevated",
+    "usage",
+  ]);
+
+  if (reservedCommands.has(trimmed)) {
     return `Command name "${trimmed}" is reserved by a built-in command`;
   }