-- Open chat with persona — file-anchored insight chat is keyed by
-- (library_id, file_path). The open chat is keyed by (user_id, persona_id)
-- with a single rolling transcript per pair. No tree branching in v1
-- (matches the locked-in "single rolling conversation per persona" scope);
-- a flat JSON blob is enough and avoids forcing a tree shape onto a
-- surface that's intentionally linear.
--
-- `messages_json` is the same `Vec<ChatMessage>` shape the file-anchored
-- chat persists, so the SSE replay / UI rendering on the mobile client
-- can reuse the same parser without a second schema.

CREATE TABLE persona_chat_conversations (
    user_id INTEGER NOT NULL,
    persona_id TEXT NOT NULL,
    messages_json TEXT NOT NULL DEFAULT '[]',
    turn_count INTEGER NOT NULL DEFAULT 0,
    updated_at BIGINT NOT NULL,
    PRIMARY KEY (user_id, persona_id)
);

CREATE INDEX idx_persona_chat_updated
    ON persona_chat_conversations (user_id, updated_at DESC);