fix(13-08): declined actions never re-prompt + timeout chain covers the human wait

Two more on-device UAT findings:

1. Deny-retry loop: the model, told 'the user declined', simply called the
   tool again — each retry minted a fresh pending and re-opened the dialog
   (T-13-50 habituation, mechanized). ToolExecCtx now remembers declined
   actions for the turn, keyed by confirm::action_key — the same canonical
   (tool_name, validated_args) identity the nonce binds — and execute_tool
   refuses a re-ask before the gate, minting nothing. Regression test
   declined_action_never_reprompts_same_turn.

2. Timeout chain: rpcClient's 15s default aborted every confirmable turn
   client-side while the node kept the pending alive — the next turn then
   re-announced it (modal over and over) and every wait read as 'timed
   out'. assistant.chat now rides a 420s timeout; AIUI's bridge goes
   180s→430s so the host's error path (which also expires the dialog)
   always fires first. Declined ToolResult text now also tells the model
   to stop.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/services/contextBroker.ts

@@ -202,9 +202,18 @@ export class ContextBroker {
     // trusted chrome can draw the dialog (see handleToolConfirmRequest).
     this.beginConfirmPolling()
     try {
+      // 13-08 UAT: a chat turn legitimately spans multiple model round
+      // trips (ASSISTANT_HTTP_TIMEOUT 180s each) plus a human-speed
+      // confirm-gate wait (CONFIRM_TIMEOUT 300s). The rpcClient default
+      // (15s) aborted every confirmable turn client-side while the node
+      // kept the pending confirmation alive — the modal then re-announced
+      // on the next turn, over and over. 420s must stay below AIUI's
+      // bridge timeout (430s) so this error, not the bridge's, is the one
+      // the user sees.
       const result = await rpcClient.call<{ text: string }>({
         method: 'assistant.chat',
         params: { text },
+        timeout: 420_000,
       })
       this.postToIframe({
         type: 'chat:response',