Fix tests to use --allowed-tools flag

Claude Code headless mode requires --allowed-tools flag to actually
execute tool calls. Without it, Claude only responds as if it's doing
things but doesn't actually use tools.

Changes:
- Updated run_claude helper to accept allowed_tools parameter
- Updated integration test to use --allowed-tools=all
- This enables actual tool execution (Write, Task, Bash, etc.)

Now the integration test should actually execute the workflow instead
of just talking about it.

tests/claude-code/test-subagent-driven-development-integration.sh

@@ -134,8 +134,9 @@ Begin now. Execute the plan.
 EOF
 
 # Note: We use a longer timeout since this is integration testing
+# Use --allowed-tools to enable tool usage in headless mode
 PROMPT=$(cat "$TEST_PROJECT/prompt.txt")
-timeout 1800 claude -p "$PROMPT" > "$OUTPUT_FILE" 2>&1 || {
+timeout 1800 claude -p "$PROMPT" --allowed-tools=all > "$OUTPUT_FILE" 2>&1 || {
     echo "EXECUTION FAILED"
     cat "$OUTPUT_FILE"
     exit 1