fix(agent-status): drop child events with whitespace-only agent ids

Review findings round 17: a whitespace-only agent_id canonicalized to
undefined and reclassified the child event as the LEAD's, minting a lead
waiting no lead Stop ever clears; agent_id-present events with an
unattributable id are now ignored. The padded-child-tool regression now
drains via a clean-id stop so it fails if canonicalization reverts.

src/shared/agent-hook-listener.test.ts

@@ -3383,16 +3383,30 @@ describe('shared agent-hook-listener', () => {
     it('routes a padded child tool event to the canonical roster row', () => {
       claudeEvent({ hook_event_name: 'UserPromptSubmit', prompt: 'go' })
       claudeEvent({ hook_event_name: 'Stop', background_tasks: [] })
-      const childTool = claudeEvent({
+      claudeEvent({
         hook_event_name: 'PreToolUse',
         agent_id: ' a4 ',
         agent_type: 'general-purpose',
         tool_name: 'Bash',
         tool_input: { command: 'true' }
       })
-      expect(childTool?.payload.subagents).toEqual([
-        expect.objectContaining({ id: 'a4', state: 'working' })
-      ])
+      // Why: a clean-id stop must drain the padded tool event's row — under a raw
+      // key it would survive and pin the lead's next Stop on working.
+      claudeEvent({ hook_event_name: 'SubagentStop', agent_id: 'a4' })
+      const leadStop = claudeEvent({ hook_event_name: 'Stop' })
+      expect(leadStop?.payload.state).toBe('done')
+      expect(leadStop?.payload.subagents).toBeUndefined()
+    })
+
+    it('ignores child events whose agent_id is whitespace-only', () => {
+      // Why: agent_id present means child-origin; an unattributable id treated
+      // as the lead would mint a waiting no lead Stop ever clears.
+      const waiting = claudeEvent({
+        hook_event_name: 'PermissionRequest',
+        agent_id: '   ',
+        tool_name: 'Bash'
+      })
+      expect(waiting).toBeNull()
     })
 
     it('tracks whitespace-padded inventory ids canonically so their stops can drain them', () => {

src/shared/agent-hook-listener.ts

@@ -2734,7 +2734,14 @@ function normalizeClaudeEvent(
 
   // Why: canonicalize like the inventory parser and lifecycle handler — a padded id must hit
   // the same roster key and wait ownership as its trimmed twin.
-  const eventAgentId = readString(hookPayload, 'agent_id')?.trim() || undefined
+  const rawAgentId = readString(hookPayload, 'agent_id')
+  const eventAgentId = rawAgentId?.trim() || undefined
+  // Why: agent_id present means child-origin by contract; a whitespace-only id cannot be
+  // attributed, and treating the event as the LEAD's would mint lead waiting/working that no
+  // lead Stop ever clears.
+  if (rawAgentId !== undefined && eventAgentId === undefined) {
+    return null
+  }
   // Why: subagent/teammate events carry `agent_id` (lead's don't); child tool activity keeps its row live but must not become the lead's state or overwrite its tool/prompt caches (a live card would vanish).
   // Two exceptions take the full path below: waiting-inducing events (a child needs human attention on this pane) and the blocked child's own next tool event (approval granted — clear the wait as for the lead).
   const isWaitingInducing = stateName === 'waiting'