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/test/spawnAtlas.source.test.js

@@ -440,6 +440,42 @@ test('decoration is read recursively and rolled up per type', () => {
   }
 })
 
+test('two spellings of one decoration type fold into one row', () => {
+  // The Phase 16 acceptance walk's blocking finding. Stock ServUO 57.4's own
+  // `Data/Decoration/` names four types under two casings each —
+  // CheckerBoard/Checkerboard, ChessBoard/Chessboard, MetalChest/Metalchest,
+  // SpinningWheelEastAddon/SpinningwheelEastAddon — and in every pair exactly one
+  // is a real class; the other is a mis-cased line the shard's own loader resolves
+  // anyway.
+  //
+  // A case-SENSITIVE Map keeps both. `shard_decor_types.type` is a PRIMARY KEY
+  // under MariaDB's default `..._ai_ci` collation, which folds case, so the second
+  // row raised `1062 Duplicate entry` and took the WHOLE atlas import transaction
+  // down with it. The blast radius is not decoration: with no atlas, EVERY option
+  // source answers empty and no world verb can be authored at all.
+  //
+  // Asserted on the count as well as the row, because the failure mode was two
+  // rows that a database — not this function — would later refuse.
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'atlas-decorcase-'))
+  try {
+    writeTree(root)
+    fs.writeFileSync(
+      path.join(root, 'Data', 'Decoration', 'miscased.cfg'),
+      'checkerboard 0x0FA6\n600 600 0\nCheckerBoard 0x0FA6\n700 700 0\n',
+    )
+    const atlas = buildAtlas(root)
+
+    const boards = atlas.decor.filter((d) => d.type.toLowerCase() === 'checkerboard')
+    assert.equal(boards.length, 1, 'two casings of one type must not be two rows')
+    // First spelling seen wins, exactly as the first item id does. Which one
+    // survives is cosmetic — the shard resolves either.
+    assert.equal(boards[0].type, 'checkerboard')
+    assert.equal(boards[0].uses, 2, 'both lines still count as uses of the one type')
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true })
+  }
+})
+
 test('a tree with no decoration at all still builds', () => {
   // Optional, like the champion file. A shard that has stripped its decoration
   // has a perfectly good atlas; the decoration verb simply has nothing to offer.