feat(bridge): lease deadlines and the participation ledger (Phase 11b)

Protocol 6 amended in place. Two mechanisms behind one new default-off gate,
`Bridge.EventsEnabled` -- deliberately not `AdminWriteEnabled`, because enabling
the admin plane is consenting to staff moderation from a screen a human is
looking at, and this is consenting to the world being changed and watched on a
schedule, unattended.

BridgeLeases: a live config value held for a bounded time, with the deadline
honoured on the shard whether or not the website is heard from again, and a
compare-and-set restore that reports `drifted` rather than overwriting a GM's
deliberate change. Memory-only -- nothing calls Config.Save() -- so a restart is
a free restore.

BridgeParticipation: presence in a declared area plus kill credit inside it,
keyed by character serial, persisted in the world save. The Bridge's first
persisted state, because a run spans hours and an in-memory tally would regress
every attendee's score after one restart. Its snapshot is also the first handler
that DEFERS, which makes `bridge.busy` reachable for the first time.

And it immediately found a defect in 11a: BridgeIdempotency.Busy built its frame
with Begin("bridge.busy") and then appended a diagnostic `.Str("kind", ...)`, so
the object carried two `kind` fields and every JSON parser takes the last. The
sidecar answered 200 instead of 425. Renamed `busyKind`.

Co-Authored-By: Claude <noreply@anthropic.com>

tools/scaffolding/README.md

@@ -14,9 +14,10 @@ These two scripts produced the measured budget in [PLAN.md](https://gitea.whitlo
 | `BridgeCrierProbe.cs` | `Scripts/Custom/BridgeCrierProbe.cs` | Logs the global town-crier entry list every 3s so `towncrier.add` / `remove` can be seen landing in game state. Flag: `CrierProbeOnStart`. |
 | `BridgeVendorSaleProbe.cs` | `Scripts/Custom/BridgeVendorSaleProbe.cs` | Fires `PlayerVendorSale` (Phase 7) with real seeded-vendor data so `vendor.sale` can be verified without a live buy. Requires the Phase 7 patches applied. Flag: `VendorSaleProbeOnStart`. |
 | `BridgeDemoDress.cs` | `Scripts/Custom/BridgeDemoDress.cs` | Renames a seeded world so it is presentable in a screenshot: shop signs, vendor and character names, house signs. Also stages a few condemned houses back into IDOC, and sets a known password on `seed_000` so a character can be logged in. Flags: `DemoDressOnStart`, `DemoDressPassword`. In game: `[demodress`. |
-| `BridgeRigDriver.cs` | `Scripts/Custom/BridgeRigDriver.cs` | Drives the shard from OUTSIDE the game, one verb per line in `Config/rigcmd.txt`, which the driver polls and truncates. Written for the engagement Phase 11b acceptance walk, where each step's assertion is 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 (`Scripts/Misc/ConsoleCommands.cs`), so `[p5probe` cannot be typed at a headless shard at all. Verbs: `decaylist`, `decay`, `vendorlist`, `vendorfunds`, `citylist`, `governor`, `election`, `activate`, `password`, `save`, `shutdown`. Flag: `RigDriverEnabled`. **Sets passwords and mutates the world.** |
+| `BridgeRigDriver.cs` | `Scripts/Custom/BridgeRigDriver.cs` | Drives the shard from OUTSIDE the game, one verb per line in `Config/rigcmd.txt`, which the driver polls and truncates. Written for the engagement Phase 11b acceptance walk, where each step's assertion is 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 (`Scripts/Misc/ConsoleCommands.cs`), so `[p5probe` cannot be typed at a headless shard at all. Verbs: `decaylist`, `decay`, `vendorlist`, `vendorfunds`, `citylist`, `governor`, `election`, `activate`, `password`, `configset`, `configread`, `partprobe`, `save`, `shutdown`. Flag: `RigDriverEnabled`. `configset` exists because **`Config.Get` is written by exactly ONE caller in the whole of ServUO 57.4** (`Server/ScriptCompiler.cs`): no in-game command, gump or console verb writes a config key, so on a stock shard a GM cannot drift a configuration lease even deliberately, and a lease's compare-and-set restore would have no way to be proved. `configread` reads a key back through `Config.Get` long after every type initialiser has run, which is how a key that TOOK is told from one that only appeared to. **Sets passwords, writes live config and mutates the world.** |
 | `BridgeProtocol5Probe.cs` | `Scripts/Custom/BridgeProtocol5Probe.cs` | Drives all three Protocol 5 enrichments so their frames can be observed: walks one house Fairly -> Greatly -> IDOC (the PAIR is the assertion -- `estimatedCollapse` must appear only on the IDOC frame), reports each player vendor's fee state straight off the `PlayerVendor` so the emitted `fees` block can be checked against the shard's own numbers, and fires `EventSink.AccountLogin`. Flags: `Protocol5ProbeOnStart`, `Protocol5ProbeAccount`, `Protocol5ProbePassword`. In game: `[p5probe`. **Sets a password on the named account.** |
 | `BridgeProtocol6Probe.cs` | `Scripts/Custom/BridgeProtocol6Probe.cs` | Spawns a real champion boss through the shard's own `SpawnChampion()`, waits two champ sweeps so the boss is attributed to its altar, registers unequal damage from two seeded players and kills it -- so `champ.boss.killed` can be observed with a real damage table. **The wait is the assertion**: without it the kill still emits, but with no `serial`/`type`/`level`, which is the documented fallback rather than the case being tested. The altar is placed inside a NAMED region on purpose (see below). Flag: `Protocol6ProbeOnStart`. In game: `[p6probe`. **Spawns and kills a champion boss; rig only.** Protocol 6's other half, the idempotency key, needs no probe -- it is driven from outside with two identical POSTs to the sidecar. |
+| `BridgeParticipationProbe.cs` | `Scripts/Custom/BridgeParticipationProbe.cs` | Produces real kill credit inside a participation area with no game client: moves two player mobiles to the venue, spawns a creature there, damages it unequally from both and kills it. **Presence is the half it cannot drive** -- the sweep credits players with a live `NetState`, which is the correct test and not one a probe should loosen, so presence accrual needs a real login. In game: `[partprobe <map> <x> <y>`; from a headless rig, through `BridgeRigDriver`'s `partprobe` verb (the two ship together for that reason). **Moves players and spawns and kills a creature; rig only.** |
 
 ## Deploy overwrites Bridge.cfg