hooks(claude): register SessionStart hook

Add SessionStart to the Claude status plugin's hook set, mirroring Codex.
A freshly started/resumed session derives to 'waiting', and its payload
carries session_id so the generic discovery in tailLog picks up the
session ID before the first prompt.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: big-guy

resources/plugins/harness-status/hooks/hooks.json

@@ -1,5 +1,16 @@
 {
   "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash -c 'h=\"$HARNESS_TERMINAL_ID\"; [ -z \"$h\" ] && h=\"$CLAUDE_HARNESS_ID\"; [ -z \"$h\" ] && exit 0; d=/tmp/harness-status; mkdir -p \"$d\"; p=$(cat); [ -z \"$p\" ] && p=null; printf \"{\\\"event\\\":\\\"SessionStart\\\",\\\"ts\\\":%s,\\\"payload\\\":%s}\\n\" \"$(date +%s)\" \"$p\" >> \"$d/$h.ndjson\"'",
+            "timeout": 5
+          }
+        ]
+      }
+    ],
     "UserPromptSubmit": [
       {
         "hooks": [

src/main/agents/claude.test.ts

@@ -158,6 +158,7 @@ describe('stripGlobalHooks (legacy migration)', () => {
 describe('hookEvents', () => {
   it('exports the events the bundled plugin must register', () => {
     expect(hookEvents).toEqual([
+      'SessionStart',
       'UserPromptSubmit',
       'PreToolUse',
       'PostToolUse',

src/main/agents/claude.ts

@@ -15,6 +15,7 @@ export const defaultCommand = 'claude'
 export const assignsSessionId = true
 
 export const hookEvents = [
+  'SessionStart',
   'UserPromptSubmit',
   'PreToolUse',
   'PostToolUse',

src/main/claude-plugin.test.ts

@@ -10,6 +10,7 @@ import { join } from 'path'
 import { makeHookCommand } from './hooks'
 
 const HOOK_EVENTS = [
+  'SessionStart',
   'UserPromptSubmit',
   'PreToolUse',
   'PostToolUse',

src/main/hooks.ts

@@ -79,6 +79,11 @@ function readPendingTool(p: Record<string, unknown> | null): PendingTool | null
 
 function deriveStatus(terminalId: string, ev: HookEvent): StatusUpdate | null {
   switch (ev.event) {
+    case 'SessionStart':
+      // Fires when a session starts or resumes. Nothing is running yet, so
+      // the tab is idle. Its payload also carries session_id, which the
+      // generic discovery in tailLog picks up before the first prompt.
+      return { status: 'waiting', pendingTool: null }
     case 'PreToolUse': {
       const tool = readPendingTool(ev.payload)
       if (tool) lastPreTool.set(terminalId, tool)