fix: Replace direct template expansion of inputs in shell scripts with environment variables (#729)

Replace direct template expansion of user inputs in shell scripts with
environment variables to prevent potential command injection attacks.

Changes:
- sync-base-action.yml: Use $GITHUB_EVENT_NAME and $GITHUB_ACTOR instead of template expansion
- action.yml: Pass path_to_bun_executable and path_to_claude_code_executable through env vars
- base-action/action.yml: Same env var changes for path inputs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

action.yml

@@ -140,10 +140,12 @@ runs:
     - name: Setup Custom Bun Path
       if: inputs.path_to_bun_executable != ''
       shell: bash
+      env:
+        PATH_TO_BUN_EXECUTABLE: ${{ inputs.path_to_bun_executable }}
       run: |
-        echo "Using custom Bun executable: ${{ inputs.path_to_bun_executable }}"
+        echo "Using custom Bun executable: $PATH_TO_BUN_EXECUTABLE"
         # Add the directory containing the custom executable to PATH
-        BUN_DIR=$(dirname "${{ inputs.path_to_bun_executable }}")
+        BUN_DIR=$(dirname "$PATH_TO_BUN_EXECUTABLE")
         echo "$BUN_DIR" >> "$GITHUB_PATH"
 
     - name: Install Dependencies
@@ -182,6 +184,8 @@ runs:
     - name: Install Base Action Dependencies
       if: steps.prepare.outputs.contains_trigger == 'true'
       shell: bash
+      env:
+        PATH_TO_CLAUDE_CODE_EXECUTABLE: ${{ inputs.path_to_claude_code_executable }}
       run: |
         echo "Installing base-action dependencies..."
         cd ${GITHUB_ACTION_PATH}/base-action
@@ -190,7 +194,7 @@ runs:
         cd -
 
         # Install Claude Code if no custom executable is provided
-        if [ -z "${{ inputs.path_to_claude_code_executable }}" ]; then
+        if [ -z "$PATH_TO_CLAUDE_CODE_EXECUTABLE" ]; then
           CLAUDE_CODE_VERSION="2.0.61"
           echo "Installing Claude Code v${CLAUDE_CODE_VERSION}..."
           for attempt in 1 2 3; do
@@ -210,9 +214,9 @@ runs:
           echo "Claude Code installed successfully"
           echo "$HOME/.local/bin" >> "$GITHUB_PATH"
         else
-          echo "Using custom Claude Code executable: ${{ inputs.path_to_claude_code_executable }}"
+          echo "Using custom Claude Code executable: $PATH_TO_CLAUDE_CODE_EXECUTABLE"
           # Add the directory containing the custom executable to PATH
-          CLAUDE_DIR=$(dirname "${{ inputs.path_to_claude_code_executable }}")
+          CLAUDE_DIR=$(dirname "$PATH_TO_CLAUDE_CODE_EXECUTABLE")
           echo "$CLAUDE_DIR" >> "$GITHUB_PATH"
         fi