docs(mcp): document Processes in server instructions

Task 3 of #582. Tells Claude that note_type=process notes are reusable saved
prompts and to fire them via list_processes/get_process on 'run the X process'.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fabledassistant/mcp/server.py

@@ -78,6 +78,13 @@ descendants) to the trash and returns a deleted_batch_id. Use list_trash() to
 see trashed batches, restore(deleted_batch_id) to undo a deletion, and
 purge_trash(deleted_batch_id, confirmed=True) for a permanent delete. Trash
 auto-purges after the operator's retention window.
+
+Scribe stores reusable Processes — saved prompts/workflows (note_type
+"process"), e.g. a drift audit or a DRY pass. When the operator says "run the
+X process" or otherwise references a saved process, call list_processes() /
+get_process(name) and follow the returned prompt verbatim, including any
+"clarify first" steps it contains. Author a new one with create_process(title,
+body); edit with update_process.
 """