feat: add pre-dispatch hook for agent task middleware

Generic extension point in community codebase: PreDispatchHook type
registered in AppState, checked before every agent_query dispatch.
Enables Pro features like budget enforcement and branch policy.

src-tauri/src/commands/agent.rs

@@ -9,6 +9,10 @@ pub fn agent_query(
     state: State<'_, AppState>,
     options: AgentQueryOptions,
 ) -> Result<(), String> {
+    // Run pre-dispatch hooks (budget enforcement, branch policy, etc.)
+    for hook in &state.pre_dispatch_hooks {
+        hook(&options)?;
+    }
     state.sidecar_manager.query(&options)
 }
 

src-tauri/src/lib.rs

@@ -29,6 +29,10 @@ use std::path::{Path, PathBuf};
 use std::sync::Arc;
 use tauri::Manager;
 
+/// Pre-dispatch hook for agent task middleware (budget enforcement, branch policy, etc.)
+/// Returns Ok(()) to allow dispatch, Err(reason) to block it.
+pub type PreDispatchHook = Box<dyn Fn(&agor_core::sidecar::AgentQueryOptions) -> Result<(), String> + Send + Sync>;
+
 pub(crate) struct AppState {
     pub pty_manager: Arc<PtyManager>,
     pub sidecar_manager: Arc<SidecarManager>,
@@ -40,6 +44,7 @@ pub(crate) struct AppState {
     pub remote_manager: Arc<RemoteManager>,
     pub search_db: Arc<search::SearchDb>,
     pub app_config: Arc<AppConfig>,
+    pub pre_dispatch_hooks: Vec<PreDispatchHook>,
     _telemetry: telemetry::TelemetryGuard,
 }
 
@@ -413,6 +418,7 @@ pub fn run() {
                 remote_manager,
                 search_db,
                 app_config: config,
+                pre_dispatch_hooks: Vec::new(),
                 _telemetry: telemetry_guard,
             });