-- 0006_chat_sender_name: tag every chat message with the human-readable sender
-- display name (DevDocs/design/16 §4.6). Group chats and stranger private chats
-- carry the sender's nickname so the agent can see who is speaking and the IM
-- adapter log page can label the message stream; the owner's private chat on the
-- main session is intentionally left blank (the owner is never labeled).
--
-- The 0005 chat_messages table already exists at this point, so ALTER ADD COLUMN is
-- the correct, non-destructive step. The canonical schema (including this column) is
-- also re-issued idempotently by internal/runtime/history.NewStore so a fresh
-- in-memory store used by tests stays self-contained; the migration is the
-- authoritative path for an existing database.

ALTER TABLE chat_messages ADD COLUMN sender_name TEXT NOT NULL DEFAULT '';