feat: add leo custom tier for personalized tool selection

- Add 'leo' tier as standalone (non-cumulative) tier
- Configure leo tier with curated tools for gmail, drive, docs, slides
- Updated tool_tier_loader to support standalone tiers
- Removed deprecated tools from leo tier (format_text_style, create_list, remove_list_formatting)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

core/tool_tiers.yaml

@@ -17,6 +17,12 @@ gmail:
     - batch_modify_gmail_message_labels
     - start_google_auth
 
+  leo:
+    - search_gmail_messages
+    - get_gmail_message_content
+    - get_gmail_messages_content_batch
+    - start_google_auth
+
 drive:
   core:
     - search_drive_files
@@ -37,6 +43,18 @@ drive:
     - get_drive_file_permissions
     - check_drive_file_public_access
 
+  leo:
+    - search_drive_files
+    - get_drive_file_content
+    - get_drive_file_download_url
+    - create_drive_file
+    - import_to_google_doc
+    - share_drive_file
+    - get_drive_shareable_link
+    - list_drive_items
+    - update_drive_file
+    - get_drive_file_permissions
+
 calendar:
   core:
     - list_calendars
@@ -72,6 +90,24 @@ docs:
     - reply_to_document_comment
     - resolve_document_comment
 
+  leo:
+    - get_doc_content
+    - create_doc
+    - modify_doc_text
+    - export_doc_to_pdf
+    - search_docs
+    - find_and_replace_doc
+    - list_docs_in_folder
+    - insert_doc_elements
+    - format_paragraph_style
+    - apply_heading_style
+    - insert_doc_image
+    - update_doc_headers_footers
+    - batch_update_doc
+    - inspect_doc_structure
+    - create_table_with_data
+    - debug_table_structure
+
 sheets:
   core:
     - create_spreadsheet
@@ -120,6 +156,13 @@ slides:
     - reply_to_presentation_comment
     - resolve_presentation_comment
 
+  leo:
+    - create_presentation
+    - get_presentation
+    - batch_update_presentation
+    - get_page
+    - get_page_thumbnail
+
 tasks:
   core:
     - get_task