adventure: work the five review findings the last pass left open

The extract pre-check is gone. It read a snapshot up to two minutes behind and
still got the last word, so somebody who set out over Matrix during a lagging
roster push was told they weren't on an expedition for a run gogobee would
happily have ended. Same call abandon and leave already made: let it through and
let rejected_not_running be the answer.

The siege_join check stays, because whether a boss is camped outside town is
town-wide and runs on a day-or-longer clock, but it now reads one column through
SiegeIsCamped instead of loading every defender row and the whole history to
look at one flag.

The war-room history insert is OR REPLACE. boss_id is the primary key and it was
never settled whether gogobee means the siege instance or the boss type by it, so
a duplicate pair used to fail the transaction carrying the live boss and the
muster too and freeze the war room on the last good snapshot. A dropped history
row is the smaller failure; the open question is noted in the schema.

offersToUndo's guard didn't cover the case its comment claimed. A gogobee too old
to push seats sends a valid blob with no party key, which decodes to the same
empty slice as a solo run, and a party member got shown the button that throws
away everyone's day. That needs a new field, so whoDetail gains party_known and
the flag gates the empty-list branch alone; the branch that reads the viewer's
own seat is self-evidencing and keeps working against any sender. gogobee's half
is written up in adventure_party_known_flag.md.

And an empty offer list no longer claims "you're already out there", which Pete
can't actually know from a game box too old to push offers at all.

internal/storage/schema.go

@@ -138,6 +138,12 @@ CREATE TABLE IF NOT EXISTS adventure_siege_defenders (
     fought_today INTEGER NOT NULL DEFAULT 0
 );
 
+-- Open question, never confirmed with gogobee: whether boss_id identifies the
+-- siege instance or the boss TYPE. SiegeBarForBoss matches history on boss_name
+-- plus the nearest ended_at and its comment says "the same boss comes back month
+-- after month", which reads like a type — in which case this key collides on the
+-- second visit. ReplaceSiege inserts OR REPLACE so a collision costs one history
+-- row instead of the whole push; settle the meaning before relying on the key.
 CREATE TABLE IF NOT EXISTS adventure_siege_history (
     boss_id      INTEGER PRIMARY KEY,
     boss_name    TEXT    NOT NULL,