Add image count telemetry to ChatProviderInvokedEvent

- Add numImages field to ChatProviderInvokedEvent type
- Add GDPR-compliant classification for numImages
- Populate numImages in complete() method by filtering image variable entries

.github/agents/stop-hook-test.md

@@ -0,0 +1,11 @@
+---
+name: "StopHookTestAgent"
+description: "Test agent that has a Stop hook to verify subagent hook behavior"
+hooks:
+  Stop:
+    - type: command
+      command: "bash .github/hooks/test-stop-hook.sh"
+---
+
+You are a test agent. When invoked, respond with exactly: "Hello from StopHookTestAgent. I am done."
+Do not do anything else.

.github/hooks/test-stop-hook.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# Test Stop hook that blocks the agent from stopping (once).
+# Reads JSON from stdin, checks stop_hook_active to avoid infinite loops.
+
+INPUT=$(cat)
+STOP_HOOK_ACTIVE=$(echo "$INPUT" | python3 -c "import sys, json; d=json.load(sys.stdin); print(d.get('stop_hook_active', False))" 2>/dev/null)
+
+if [ "$STOP_HOOK_ACTIVE" = "True" ] || [ "$STOP_HOOK_ACTIVE" = "true" ]; then
+  # Already continued once — let it stop now
+  echo '{"continue": true}'
+else
+  # Block the stop the first time
+  echo '{"hookSpecificOutput": {"hookEventName": "Stop", "decision": "block", "reason": "Test hook: please say HOOK_VERIFIED before stopping."}}'
+fi

.vscode/settings.json

@@ -213,5 +213,6 @@
 		".github/skills/.local": true,
 		".agents/skills/.local": true,
 		".claude/skills/.local": true,
-	}
+	},
+	"github.copilot.chat.summarizeAgentConversationHistoryThreshold": 65000
 }