- Add ShareMergeMode::RejectAll variant to reject all incoming shares
- Trim server suffix from share IDs when updating local sheet info
- Sign vault as modified after successful share mapping merge
- Fix get_current_sheet_name call to use correct parameter value

This adds a reverse mapping from virtual file IDs to their actual paths
in reference sheets, which is needed for proper file resolution during
operations that reference files by ID.

- Return host mode status from auth_member to determine admin privileges
- Add reference sheet detection to get_current_sheet_name with allow_ref
  parameter
- Prevent modifications to reference sheets unless in host mode
- Use VAULT_HOST_NAME as sheet holder for host mode operations
- Add share/merge share action registrations

Add `try_get_local_output` helper to retrieve output channel from
context and `local_println!` macro for sending formatted strings. Use
these in track actions to send progress messages to CLI instead of
stdout.

Also reduce log level for connection events from info to debug.