Phase 3: polled sweeps (vitals, house decay, economy)

BridgeSweeps runs three repeating Core-thread timers for the state that has no
EventSink. Cost measured in Phase 1 is why they can run on the main thread: a
full pass of all three is well under a millisecond at the seeded scale.

  - Vitals: online players only. Small and volatile; the sidecar diffs snapshots.
    Offline characters do not move, so they are served on demand as full profiles
    instead, not swept.
  - House decay: emits only on a level transition. A silent baseline on
    ServerStarted records every house's current stage, so a restart does not
    re-announce them. Payload carries from/to, coords, nested ban location,
    region, sign name, owner serial+account, and built/refreshed timestamps, all
    null-guarded.
  - Economy supply: periodic sum of every account's currency as a snapshot. The
    level; AccountGoldChange and the vendor events are the flow.

All three re-arm on `[bridge reload`; `[bridge sweepnow` runs one of each on
demand; `[bridge status` reports sweep counters. Sweeps skip emitting while the
sidecar is disconnected, since their state is perishable and re-emitted next
tick anyway (unlike events, which queue through an outage).

Verified on the seeded world with 8s intervals: baseline recorded 29 houses
silently, a probe bumped one Somewhat->Fairly, and the next sweep emitted exactly
one house.decay and none for the other 28. Economy emitted a supply snapshot per
interval. Vitals emitted nothing, correctly, since all seeded characters are
offline. Evidence in docs/PLAN.md §13.

Adds tools/scaffolding/BridgeSweepProbe.cs (never deployed) to force a decay
transition on demand.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

link/PLAN.md

@@ -305,7 +305,7 @@ Counts in `hello` are a live snapshot taken on the Core thread, not a cached val
 0. ~~**Fix the build** (§3).~~ **Done.** Verified: a plain boot now logs `Core: Compiling scripts... / Build succeeded.`
 1. ~~**Transport.**~~ **Done.** `BridgeLink`: `TcpClient`, link thread + bounded drop-oldest queue, reader thread → `Timer.DelayCall`, reconnect with backoff capped at 5 s. Emits `server.hello` / `server.shutdown` / `server.crashed`, answers `ping` with `pong`. `[bridge status|reload|ping]`. Acceptance evidence in §11.
 2. ~~**Cheap event streams.**~~ **Done.** `BridgeEvents` subscribes the streams selected below. All observed on the live shard; evidence in §12.
-3. **Sweeps.** Vitals (30 s), decay-on-transition (60 s, with silent `ServerStarted` baseline), economy supply (5 min). All config-tunable; `[bridge reload` re-arms the timers.
+3. ~~**Sweeps.**~~ **Done.** `BridgeSweeps`: vitals / decay-on-transition / economy, all Core-thread timers, re-armable. Evidence in §13.
 4. **Request/response.** `char.profile`, `account.roster`, `vendor.snapshot`. Sidecar caches profiles; rate-limit requests sidecar-side.
 5. **`[link` account linking.** `CommandSystem.Register("link", AccessLevel.Player, …)`, one-time short-TTL codes in a main-thread dict, `Account.SetTag("WebsiteUserId", id)` — persists to `accounts.xml` for free. Loopback-only is the trust boundary; add a shared secret if the sidecar is ever exposed.
 6. **Town-crier inbound.** `GlobalTownCrierEntryList.Instance.AddEntry(lines, duration)` (`Scripts/Mobiles/NPCs/TownCrier.cs:96`), marshaled to the Core thread. Cap line count/length and active entries.
@@ -348,6 +348,32 @@ Two defects were found this way and fixed:
 
 ---
 
+## 13. Phase 3 acceptance
+
+`BridgeSweeps.cs` runs three repeating Core-thread timers: vitals (`StatSweepSeconds`), house decay (`DecaySweepSeconds`), economy supply (`EconomySweepSeconds`). All re-armable via `[bridge reload`; `[bridge sweepnow` runs one of each on demand; `[bridge status` reports sweep counters.
+
+Verified on the seeded world with intervals cut to 8 s:
+
+- **Decay is transition-only.** Baseline recorded 29 houses **silently** on `ServerStarted`. A probe bumped one house `Somewhat → Fairly` with `SetDynamicDecay`; the next sweep emitted **exactly one** `house.decay`, none for the other 28:
+
+  ```json
+  {"kind":"house.decay","serial":"0x4004705F","from":"Somewhat","to":"Fairly",
+   "map":"Trammel","x":1119,"y":1794,"z":0,"region":null,"name":"An Unnamed House",
+   "ownerSerial":"0x75","ban":{"x":1112,"y":1804,"z":0},
+   "builtOn":"2026-05-11T…","lastRefreshed":"2026-05-31T…"}
+  ```
+
+- **Economy supply** emitted a snapshot each interval: `{"kind":"economy.supply","accounts":51,"gold":…}`.
+- **Vitals** correctly emitted nothing — the seeded characters are all offline (`NetState == null`). The JSON shape is the same field set proven by the Phase 1 probe; the online-emission path is not exercised without a live client.
+
+Notes from the run:
+
+- **`region` is null** for the seeded houses — they sit outside any named region. The handler guards `Region`, `Sign`, and `Owner` for null; all three can be absent on abandoned or oddly-placed houses.
+- The sweeps **skip emitting when the sidecar is disconnected** (`BridgeLink.Connected`), so a long outage does not fill the bounded queue with perishable snapshots. Events (Phase 2) still queue through an outage because they are not perishable; sweeps re-emit fresh state on the next tick regardless.
+- **Config duplicate keys: last write wins** (`Config.cs` does `_Entries[key] = e`), which is why the scaffolding appends test overrides to the end of `Bridge.cfg`.
+
+---
+
 ## 12. Phase 2 acceptance
 
 The selected streams (`Login`, `Logout`, `AccountLogin`, `AccountGoldChange`, `ValidVendorPurchase`/`Sell`, `PlacePlayerVendor`, `SkillGain`, `FameChange`, `KarmaChange`, `QuestComplete`, `PlayerDeath`, `PlayerMurdered`, `OnKilledBy`, `FastWalk`, `OnPropertyChanged`, `Command`, `Before`/`AfterWorldSave`) are in `BridgeEvents.cs`. Gold, fame, karma, and the save boundaries were fired through their real code paths (`DepositGold`, the `Fame`/`Karma` setters, `World.Save()`) and observed at the stub sidecar: