fix(events): the atlas import, and a teardown that was a no-op (Phase 16a)

Two defects the acceptance walk found in shipped code, both invisible to the
suites that were green on either side of them.

**The spawn atlas cannot import on a stock ServUO tree.** `spawnAtlasSource.js`
dedupes decoration types with a case-SENSITIVE `Map`, but `shard_decor_types.type`
is a PRIMARY KEY under MariaDB's default `..._ai_ci` collation, which folds case.
Stock 57.4's own `Data/Decoration/` names four types under two spellings each
(CheckerBoard/Checkerboard, ChessBoard/Chessboard, MetalChest/Metalchest,
SpinningWheelEastAddon/SpinningwheelEastAddon), and in every pair exactly one is a
real class. The second row raised `1062 Duplicate entry` and took the WHOLE import
transaction down. The blast radius is not decoration: with no atlas, EVERY option
source answers empty and no Phase 12 world verb can be authored at all.

The shard end already knew — `BridgeWorld.cs` resolves a decor type with
`FindTypeByName(name, ignoreCase: true)` and its comment says the atlas and the
decoration files disagree about casing. Folding here is the two ends agreeing.

**Teardown of every world verb was a no-op that reported success.** `revertOwned`
forwarded core's `idempotencyKey` as the despawn's OWN key — and core's key is the
step's, the one `placeOwned` spawned under. `BridgeIdempotency` keys on the key
alone, so the despawn was taken for a repeat and answered with the SPAWN's stored
reply; `OnDespawn` never ran. Core read `ok` with no `refused` and marked every
row `reverted` while the shard still held every object.

Measured on the rig: ledger `world | reverted | 21`, shard `world.owned` 21 alive
with `pruned: 0`, and the identical despawn re-sent with a fresh key removed all
21. It affected all five world verbs, so an invasion's creatures, boss, oracle,
gate and decoration stayed in the world for ever while the console reported a
clean teardown.

`MODULE_API.md` says what that key is for and it is not this: it identifies a
dispatch core never learned the outcome of, so the module can ask about it. No key
is needed on a despawn — a repeat answers `gone`, which both ends already treat as
success — and dropping it also makes the documented empty-`resources` case work,
since no serials means "everything this run owns". The parameter is removed from
`despawnWorld`'s signature rather than left optional.

Both fixes are verified end to end against a real ServUO + sidecar + website rig:
the import now yields 309 decor types (was failing at 313 with 4 collisions),
6,455 spawn points, 800 creatures, 558 landmarks; and a full four-phase run's
teardown left the shard owning 0 objects.

Each new test was confirmed to FAIL without its fix.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4

server/utils/spawnAtlasSource.js

@@ -336,11 +336,29 @@ function buildAtlas(root, options = {}) {
 
   // Decoration: what this shard already calls scenery, which is what makes the
   // authoring dropdown the operator's own vocabulary rather than our taste.
+  //
+  // **Keyed case-INSENSITIVELY, because the decoration files disagree with
+  // themselves about casing.** Stock 57.4 names four types under two spellings
+  // each — `CheckerBoard`/`Checkerboard`, `ChessBoard`/`Chessboard`,
+  // `MetalChest`/`Metalchest`, `SpinningWheelEastAddon`/`SpinningwheelEastAddon`
+  // — and in every pair exactly one is a real class, the other a mis-cased line
+  // the shard's own loader resolves anyway. A case-sensitive Map keeps both, and
+  // then `shard_decor_types.type` (a PRIMARY KEY under MariaDB's default
+  // `..._ai_ci` collation, which folds case) rejects the second row and takes the
+  // WHOLE import transaction down with it. That is not a decoration bug: with no
+  // atlas, every option source answers empty and no world verb can be authored at
+  // all. The shard end of this feature already knew — `BridgeWorld.cs` resolves a
+  // decor type with `FindTypeByName(name, ignoreCase: true)` and says why — so
+  // folding here is the two ends agreeing rather than a new rule.
+  //
+  // The first spelling seen wins, exactly as the first item id does. Either
+  // spelling resolves on the shard, so which one survives is cosmetic.
   const decorUses = new Map()
   for (const file of files) {
     if (!file.label.startsWith('Data/Decoration/')) continue
     for (const entry of parseDecoration(file.text)) {
-      const seen = decorUses.get(entry.type)
+      const key = entry.type.toLowerCase()
+      const seen = decorUses.get(key)
       if (seen) {
         seen.uses += 1
         continue
@@ -348,7 +366,7 @@ function buildAtlas(root, options = {}) {
       // The FIRST item id wins, and it is only a preview: a type appears under
       // as many ids as it has facings or variants, and picking one arbitrarily
       // is honest in a way that picking "the most used" would not be.
-      decorUses.set(entry.type, { type: entry.type, itemId: entry.itemId, uses: 1 })
+      decorUses.set(key, { type: entry.type, itemId: entry.itemId, uses: 1 })
     }
   }
   const decor = [...decorUses.values()].sort((a, b) => a.type.localeCompare(b.type))