The recent-dialogue read and the directed-pair edge gather were
duplicated between ``chat.services.regenerate`` and ``chat.web.turns``.
Extracted into ``chat.services.turn_common`` with two helpers:
- ``read_recent_dialogue(conn, chat_id, *, limit, exclude_event_id)``:
oldest-first ``[{speaker, text}]`` over user_turn / user_turn_edit /
assistant_turn rows, with the standard ``superseded_by IS NULL AND
hidden = 0`` filter. ``exclude_event_id`` covers regenerate's need to
drop the original assistant_turn before its supersede UPDATE lands.
- ``gather_prior_edges(conn, present_ids)``: ``{(src, tgt): edge}`` over
every directed pair across ``present_ids``, with the schema default
50/50 baseline for missing rows.
``chat.web.turns._read_recent_dialogue`` becomes a thin delegate so the
chat-detail template and other in-module callers keep their import
shape; ``_gather_state_update_inputs`` now calls into the shared edge
gather. ``regenerate_assistant_turn`` calls both helpers in three call
sites (primary + post-interjection edges, primary + interjection
recent reads), still post-processing speaker ids to display names for
its prompts.
Decision: ``chat.services.scene_summarize._read_recent_dialogue`` is
left in place — it has a ``since_event_id`` clamp (T80.2) and excludes
``user_turn_edit`` deliberately. Folding it into the shared helper
would either silently change its read shape or require a second flag,
both more invasive than the duplication. Documented in the new module
docstring.
Tests: tests/test_turn_common.py covers chronological ordering,
supersede / other-chat / exclude_event_id filtering, and prior-edge
default-fallback. Existing 6 regenerate + 18 turn_flow tests pass
unchanged.
Joseph Doherty