chore: Disable scheduled GitHub Actions workflows in forks

Add repository checks to prevent scheduled workflows from running
in forked repositories. This prevents excessive notifications from
periodic workflow runs (every 6 hours for triage, daily for stale-bot
and docs upload) in forks where they are not needed.

The workflows will now only run in the main google/adk-python repository.

Author: ftnext

.github/workflows/stale-bot.yml

@@ -23,6 +23,7 @@ on:
 
 jobs:
   audit-stale-issues:
+    if: github.repository == 'google/adk-python'
     runs-on: ubuntu-latest
     timeout-minutes: 60
 

.github/workflows/triage.yml

@@ -15,9 +15,11 @@ jobs:
     # - New issues (need component labeling)
     # - Issues labeled with "planned" (need owner assignment)
     if: >-
-      github.event_name == 'schedule' ||
-      github.event.action == 'opened' ||
-      github.event.label.name == 'planned'
+      github.repository == 'google/adk-python' && (
+        github.event_name == 'schedule' ||
+        github.event.action == 'opened' ||
+        github.event.label.name == 'planned'
+      )
     permissions:
       issues: write
       contents: read

.github/workflows/upload-adk-docs-to-vertex-ai-search.yml

@@ -9,6 +9,7 @@ on:
 
 jobs:
   upload-adk-docs-to-vertex-ai-search:
+    if: github.repository == 'google/adk-python'
     runs-on: ubuntu-latest
 
     steps: