Remove pull-request/* branches trigger event references from CI documentation

Co-authored-by: leofang <5534781+leofang@users.noreply.github.com>

Author: Copilot

CONTRIBUTING.md

@@ -101,7 +101,7 @@ Alternative Mermaid diagram representation:
 flowchart TD
     %% Trigger Events
     subgraph TRIGGER["🔄 TRIGGER EVENTS"]
-        T1["• Push to main branch<br/>• Push to pull-request/* branches"]
+        T1["• Push to main branch"]
         T2["• Pull request<br/>• Manual workflow dispatch"]
         T1 --- T2
     end

ci/.ci-pipeline-regen.md

@@ -22,7 +22,6 @@ This file contains the prompt and requirements for regenerating `ci-pipeline.svg
 2. **Trigger Events** (top blue box):
    - Push to main branch
    - Pull request
-   - Push to pull-request/* branches
    - Manual workflow dispatch
 
 3. **Build Stage** (purple box):