Add version management, metrics, and trigger code generation tools

New tools added:
- delete_script_project: Full CRUD support for script projects
- list_versions: List all versions of a script
- create_version: Create immutable version snapshots
- get_version: Get details of a specific version
- get_script_metrics: Get execution analytics (active users, executions, failures)
- generate_trigger_code: Generate Apps Script code for time-based and event triggers

Changes:
- Updated auth/scopes.py with script.metrics scope and drive.file for delete
- Updated core/tool_tiers.yaml with new tools in core and extended tiers
- Updated gappsscript/README.md with new features documentation
- Added 8 new unit tests (18 total)

This brings total Apps Script tools from 11 to 17, covering the complete REST API.

auth/scopes.py

@@ -76,6 +76,7 @@ SCRIPT_DEPLOYMENTS_READONLY_SCOPE = (
 SCRIPT_PROCESSES_READONLY_SCOPE = (
     "https://www.googleapis.com/auth/script.processes"
 )
+SCRIPT_METRICS_SCOPE = "https://www.googleapis.com/auth/script.metrics"
 
 # Base OAuth scopes required for user identification
 BASE_SCOPES = [USERINFO_EMAIL_SCOPE, USERINFO_PROFILE_SCOPE, OPENID_SCOPE]
@@ -118,7 +119,8 @@ SCRIPT_SCOPES = [
     SCRIPT_DEPLOYMENTS_SCOPE,
     SCRIPT_DEPLOYMENTS_READONLY_SCOPE,
     SCRIPT_PROCESSES_READONLY_SCOPE,  # Required for list_script_processes
-    DRIVE_READONLY_SCOPE,  # Required for list_script_projects (uses Drive API)
+    SCRIPT_METRICS_SCOPE,  # Required for get_script_metrics
+    DRIVE_FILE_SCOPE,  # Required for list/delete script projects (uses Drive API)
 ]
 
 # Tool-to-scopes mapping