Move deleted files to trash by default instead of hard-deleting (#304)

DELETE previously called adapter.remove(), permanently destroying the
file and bypassing the user's Obsidian "Deleted files" preference.
DELETE on /vault/{path}, /active/, and /periodic/... now moves files
to trash via FileManager.trashFile() by default; a new ?permanent=true
query parameter (and matching MCP vault_delete `permanent` argument)
restores the old irrecoverable behavior. This is a default-behavior
change, hence targeting the 5.0 major bump.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>