`BridgeMarket.Signature()` diffs shop name, owner, map, coordinates and the
item/price list -- the things a LISTING is made of. Protocol 5 added a `fees`
block to the frame and the change detector never learned about it.
So a vendor quietly running down its gold altered nothing the sweep compared,
emitted no frame, and `uo.vendor.expiring` -- the notification whose entire
subject is a vendor running out of gold -- could fire only by coincidence: when
somebody happened to reprice an item on a shop that was already broke. Proved on
the engagement Phase 11b live rig by setting a vendor's held gold to zero and
watching no frame follow.
The signature carries the DERIVED values, `exempt` and `periodsRemaining`, not
the raw ones. An integer division moves only when the shard's own answer to "is
this vendor in danger" moves; `HoldGold` changes on every sale and `NextPayTime`
on every tick, and keying on either would re-emit a fat listing frame for a shop
whose listings had not changed.
Emit CADENCE, not frame shape: no field added, PROTOCOL_VERSION untouched, and
`overlay.toml` unchanged. The general form is worth carrying forward -- a
sweep-based kind has a change detector, and a field added to the frame but not to
the detector ships correct and arrives never.
Also adds `tools/scaffolding/BridgeRigDriver.cs`: the shard driven from outside
the game over a polled command file. A walk asserts what happened BETWEEN two
steps, so the steps have to be separated by the observer rather than by a
hard-coded delay -- and ServUO's console takes a fixed verb set, so `[p5probe`
cannot be typed at a headless shard at all. Never deployed; `deploy.ps1` copies
only `overlay/`. The README gains the two ServUO facts the walk cost a rebuild
each to learn: a condemned house cannot be refreshed, and only a clean shutdown
emits.
Co-Authored-By: Claude <noreply@anthropic.com>
