refactor: implement proper ACP session modes and fix type safety

Replace client-side permission mode hack with proper ACP session modes:
- Add typed Client interface implementation to ACPClient
- Import proper types from ACP SDK (SessionNotification, RequestPermissionRequest, etc.)
- Fix critical sessionUpdate bug where params.update was undefined
- Replace PermissionMode with SessionMode from ACP spec
- Add getCurrentMode(), getAvailableModes(), setSessionMode() to AgentManager
- Update MCP tools: replace set_agent_permission_mode with set_agent_mode
- Add session_state message type to send live agents/commands to client
- Update UI to display session mode badges (ask/code/architect)
- Remove all permissionsMode references from tests

Agents now have ONE mode (session mode) that controls their behavior,
system prompts, and tool availability - not separate permission/session modes.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

packages/voice-assistant/src/server/messages.ts

@@ -123,6 +123,12 @@ export const AgentCreatedMessageSchema = z.object({
     agentId: z.string(),
     status: z.string(),
     type: z.literal("claude"),
+    currentModeId: z.string().optional(),
+    availableModes: z.array(z.object({
+      id: z.string(),
+      name: z.string(),
+      description: z.string().nullable().optional(),
+    })).optional(),
   }),
 });
 
@@ -151,6 +157,38 @@ export const AgentStatusMessageSchema = z.object({
   }),
 });
 
+export const SessionStateMessageSchema = z.object({
+  type: z.literal("session_state"),
+  payload: z.object({
+    agents: z.array(
+      z.object({
+        id: z.string(),
+        status: z.string(),
+        createdAt: z.date(),
+        type: z.literal("claude"),
+        sessionId: z.string().optional(),
+        error: z.string().optional(),
+        currentModeId: z.string().optional(),
+        availableModes: z.array(z.object({
+          id: z.string(),
+          name: z.string(),
+          description: z.string().nullable().optional(),
+        })).optional(),
+      })
+    ),
+    commands: z.array(
+      z.object({
+        id: z.string(),
+        name: z.string(),
+        workingDirectory: z.string(),
+        currentCommand: z.string(),
+        isDead: z.boolean(),
+        exitCode: z.number().nullable(),
+      })
+    ),
+  }),
+});
+
 export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   ActivityLogMessageSchema,
   AssistantChunkMessageSchema,
@@ -162,6 +200,7 @@ export const SessionOutboundMessageSchema = z.discriminatedUnion("type", [
   AgentCreatedMessageSchema,
   AgentUpdateMessageSchema,
   AgentStatusMessageSchema,
+  SessionStateMessageSchema,
 ]);
 
 export type SessionOutboundMessage = z.infer<
@@ -179,6 +218,7 @@ export type ConversationLoadedMessage = z.infer<typeof ConversationLoadedMessage
 export type AgentCreatedMessage = z.infer<typeof AgentCreatedMessageSchema>;
 export type AgentUpdateMessage = z.infer<typeof AgentUpdateMessageSchema>;
 export type AgentStatusMessage = z.infer<typeof AgentStatusMessageSchema>;
+export type SessionStateMessage = z.infer<typeof SessionStateMessageSchema>;
 
 // Type exports for payload types
 export type ActivityLogPayload = z.infer<typeof ActivityLogPayloadSchema>;