fix(ci): only auto-review on PR opened, not synchronize

Removes synchronize trigger to prevent cancel-on-push issue.
Reviews now trigger:
- Auto: when PR is first opened
- Manual: via /review comment
- Manual: via workflow_dispatch

This prevents pushes from cancelling in-progress reviews.
Must be on main for pull_request_target to use updated workflow.

.github/workflows/ai-review.yml

@@ -3,14 +3,15 @@
 # Posts as ccs-agy-reviewer[bot] via GitHub App
 #
 # Triggers:
-# - Automatically on PR open/update
+# - Automatically when PR is first opened
 # - Manually via /review comment on PR
+# - Manually via workflow_dispatch
 
 name: AI Code Review
 
 on:
   pull_request_target:
-    types: [opened, synchronize, reopened]
+    types: [opened]  # Only on first open, not synchronize (avoids cancel-on-push)
   issue_comment:
     types: [created]
   workflow_dispatch:
@@ -20,7 +21,7 @@ on:
         required: true
         type: string
 
-# Cancel in-progress runs for same PR
+# Cancel in-progress runs for same PR (safe now since auto-trigger is only on opened)
 concurrency:
   group: ai-review-${{ github.event.pull_request.number || github.event.issue.number || github.event.inputs.pr_number }}
   cancel-in-progress: true
@@ -36,7 +37,7 @@ jobs:
       id-token: write
 
     # Conditions:
-    # - PR event: always run (pull_request_target has secrets access for forks)
+    # - PR event: only on opened (not synchronize to avoid cancel-on-push)
     # - Comment event: only if it's a PR and contains /review
     if: >
       github.event_name == 'pull_request_target' ||