fix(local-agent): handle empty-string hook_event_name from STDIN

[m0Nst3r873]

Summary

• Replace ??= with falsy check for hookData.hook_event_name, so empty strings from STDIN are correctly overwritten with the CLI-derived event name
• Fixes org-binding prompts and all event-gated logic not triggering on WorkBuddy and CodeBuddy

Root Cause

WorkBuddy/CodeBuddy pass hook_event_name: "" in the hook STDIN JSON payload. The ??= operator only overwrites null/undefined, not empty string "". So the empty value was kept, parseHookEvent returned null (mapEventType("") → null), and context.event stayed undefined — causing ensureWorkspaceBinding (session_start) and emitBindingHint (prompt_submit) to be skipped.

Fix

- hookData.hook_event_name ??= hookEventName(eventName);
+ if (!hookData.hook_event_name) hookData.hook_event_name = hookEventName(eventName);

1 line change. Empty string is now treated the same as missing — the event name derived from the CLI argument (session-start → SessionStart, etc.) takes over.

Test plan

• On WorkBuddy: open a new project, verify org-binding prompt appears
• On CodeBuddy: same verification
• debug.log should show [xxxxxx] [workbuddy] tags (local-agent path) instead of [status-report] tags
• npx tsc --noEmit passes

🤖 Generated with Claude Code