feat(session): validate agents and browse workspace directories

shared/src/apiTypes.ts

@@ -130,7 +130,12 @@ export type MachinesResponse = { machines: Machine[] }
 
 export type SpawnResponse =
     | { type: 'success'; sessionId: string }
-    | { type: 'error'; message: string }
+    | {
+        type: 'error'
+        message: string
+        code?: 'agent_unavailable' | 'runner_upgrade_required' | 'outside_workspace_roots'
+        agent?: z.infer<typeof AgentFlavorSchema>
+    }
 
 export const SessionPermissionModeRequestSchema = z.object({
     mode: PermissionModeSchema
@@ -633,6 +638,21 @@ export const MachinePathsExistsRequestSchema = z.object({
 
 export type MachinePathsExistsRequest = z.infer<typeof MachinePathsExistsRequestSchema>
 
+export const AgentAvailabilityReasonSchema = z.enum(['not_found', 'invalid_configuration'])
+export type AgentAvailabilityReason = z.infer<typeof AgentAvailabilityReasonSchema>
+
+export const AgentAvailabilityEntrySchema = z.object({
+    agent: AgentFlavorSchema,
+    available: z.boolean(),
+    reason: AgentAvailabilityReasonSchema.optional()
+})
+export type AgentAvailabilityEntry = z.infer<typeof AgentAvailabilityEntrySchema>
+
+export const AgentAvailabilityResponseSchema = z.object({
+    agents: z.array(AgentAvailabilityEntrySchema)
+})
+export type AgentAvailabilityResponse = z.infer<typeof AgentAvailabilityResponseSchema>
+
 export const AuthRequestSchema = z.union([
     z.object({ initData: z.string() }),
     z.object({ accessToken: z.string() })
@@ -716,6 +736,8 @@ export type MachineListDirectoryResponse = {
 
 export type PathExistsResponse = {
     exists: Record<string, boolean>
+    /** Requested paths rejected by the runner's configured workspace roots. */
+    outsideWorkspaceRoots?: string[]
 }
 
 export type MachinePathsExistsResponse = PathExistsResponse