Let Hub continue agents through the standard daemon API (#4354)

* feat(hub): continue agents through standard daemon operations

Authorize ordinary agent and workspace recovery operations with hub.execute. Keep conversation routing in Hub and persist generic creation and message receipts so retries cannot silently duplicate work.

* fix(hub): expose custom providers to continuing clients

Allow Hub to advertise provider support independently of the app version. Document the companion continuation policy and migration. Preserve newly observed files in the native watcher inventory so coalesced deletions remain visible to reconciliation, addressing the Windows CI failure.

* fix(hub): allow retries after confirmed local failures

Prepare message loading before recording dispatch intent. Remove failed creation receipts only when creation cleanup completed and no live or stored agent exists. Keep ambiguous provider deliveries fail-closed. Exercise native file observation with real filesystem dependencies.

packages/protocol/src/client-capabilities.ts

@@ -1,4 +1,6 @@
 export const CLIENT_CAPS = {
+  // Clients outside the Paseo app version series can explicitly accept provider IDs.
+  allProviders: "all_providers",
   // COMPAT(selectiveAgentTimeline): added in v0.1.106. Capable clients receive
   // agent streams only for their explicit viewed set. Remove after 2027-01-12
   // once the supported client floor is >= v0.1.106.

packages/protocol/src/messages.ts

@@ -1677,6 +1677,8 @@ export type CreateAgentWorktreeTarget = z.infer<typeof CreateAgentWorktreeTarget
 
 export const CreateAgentRequestMessageSchema = z.object({
   type: z.literal("create_agent_request"),
+  // A creation key requires initialPrompt to be sent separately with a stable messageId.
+  idempotencyKey: z.string().min(1).max(512).optional(),
   config: AgentSessionConfigSchema,
   env: z.record(z.string(), z.string()).optional(),
   workspaceId: z.string().optional(),
@@ -3399,6 +3401,10 @@ export const ServerInfoStatusPayloadSchema = z
     // COMPAT(providersSnapshot): added in v0.1.48, remove gating when all clients use snapshot
     features: z
       .object({
+        // COMPAT(agentRequestReceipts): added in v0.7.3; remove gate after 2027-03-05.
+        agentRequestReceipts: z.boolean().optional(),
+        // COMPAT(hubAgentRpc): added in v0.7.3; remove gate after 2027-03-05.
+        hubAgentRpc: z.boolean().optional(),
         providersSnapshot: z.boolean().optional(),
         // COMPAT(providersSnapshotCwd): added in v0.3.2, remove gate after 2027-02-10.
         providersSnapshotCwd: z.boolean().optional(),
@@ -7078,6 +7084,7 @@ export const WSHelloMessageSchema = z.object({
     .object({
       voice: z.boolean().optional(),
       pushNotifications: z.boolean().optional(),
+      [CLIENT_CAPS.allProviders]: z.boolean().optional(),
       [CLIENT_CAPS.reasoningMergeEnum]: z.boolean().optional(),
       [CLIENT_CAPS.selectiveAgentTimeline]: z.boolean().optional(),
       [CLIENT_CAPS.customModeIcons]: z.boolean().optional(),