Rename install-bun.py to install-bun to avoid CodeQL python analysis

The .py extension triggered a separate CodeQL python job that always
failed. The script still runs via python3 explicitly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

.github/workflows/main-build.yml

@@ -19,7 +19,7 @@ jobs:
       # Install Bun directly — avoids `apt-get update` (9+ min in this
       # container) which setup-bun needs for unzip.
       - name: Install Bun
-        run: python3 tools/install-bun.py
+        run: python3 tools/install-bun
 
       - name: Install dependencies
         run: bun install --frozen-lockfile

.github/workflows/test-headless.yml

@@ -22,7 +22,7 @@ jobs:
       # Install Bun directly — avoids `apt-get update` (9+ min in this
       # container) which setup-bun needs for unzip.
       - name: Install Bun
-        run: python3 tools/install-bun.py
+        run: python3 tools/install-bun
 
       - name: Install dependencies
         run: bun install --frozen-lockfile