Extends the reconnect re-seeding fix to work cleanly on Gemini Live 2.5,
which has stricter seed requirements than 3.x and a documented audio-input /
history-recall limitation. Both initial connection and reconnect now share a
single code path (`_create_initial_response(for_reconnect=...)`), with four
well-documented cases.
On Gemini 2.5 reconnect, `turn_complete=True` is now forced on the seed so
the model produces a recap-style response immediately instead of briefly
acting "forgetful" on the user's next utterance — the latter being
especially jarring mid-conversation. When a 2.5 seed doesn't already end
with a user turn (e.g. the bot had finished speaking before the disconnect),
a blank user turn is appended to satisfy the server's seed-shape
requirement. Gemini 3.x needs neither workaround.
