test(client): check what the chunk registers, and fix two defects in the checks

Three things, all about checks that had never met a real chunk.

`checkExternals.js` rejected slice 3's build outright, naming a fragment of
minified JSX as an imported specifier: a button reading "Approve and import"
puts the token immediately before a quote, and no regexp can tell that from a
statement. Same wall the server's `checkImports.js` hit, answered the same way —
a character walk. A mask rather than a rewrite, because a real import has its
keyword outside a string and its specifier inside one.

Writing the test for that false positive found the false NEGATIVE underneath
it: the pattern required whitespace after `import`, so it could not see
`import{useState}from"react"` — the one shape a minified build actually emits,
and the most likely way for a missed alias to reach production. It has never
been able to see it.

`registration.test.js` is new: stand up a fake `window.__rg` with a recording
registry and the real React, import the BUILT chunk, and read back what it
asked for. No DOM, because nothing renders. It holds the agreement that rots
quietly — every nav row points at a route this module actually registered —
rather than restating both lists.

CI now builds before it tests, because both of those read `dist/entry.js` and
skip without it. Run the other way round they are green and asking nothing.

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

client/test/regionBuckets.test.js

@@ -0,0 +1,60 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { bucketize, BUCKETS } from '../src/data/regionBuckets.js'
+
+// Unit-test the presence.online region roll-up for the "Players Online" widget.
+// The load-bearing invariant: the bucket counts ALWAYS reconcile to the true
+// total — anything unmatched lands in Wilderness — so the widget can never show
+// a sum that disagrees with the headline online count.
+
+test('bucketize groups named regions into their buckets', () => {
+  const { rows, total } = bucketize({
+    'Britain': 4,
+    'Moonglow': 2,
+    'Despise': 3,
+    'Green Acres House 12': 1, // not a town/dungeon name → Housing
+  })
+  const byId = Object.fromEntries(rows.map((r) => [r.id, r.count]))
+  assert.equal(byId.britain, 4)
+  assert.equal(byId.towns, 2)
+  assert.equal(byId.dungeons, 3)
+  assert.equal(byId.housing, 1)
+  assert.equal(total, 10)
+})
+
+test('first match wins by BUCKETS order: a town-named house region counts as Towns, not Housing', () => {
+  // The towns regex is ^-anchored and towns is checked BEFORE housing, so a house
+  // region whose name starts with a town name is bucketed as Towns. Pinning this
+  // documents the ordering dependency for anyone retuning BUCKETS.
+  const { rows } = bucketize({ 'Trinsic House 12': 1 })
+  const byId = Object.fromEntries(rows.map((r) => [r.id, r.count]))
+  assert.equal(byId.towns, 1)
+  assert.equal(byId.housing, undefined) // empty bucket dropped
+})
+
+test('an unmatched region falls through to Wilderness so counts always reconcile', () => {
+  const { rows, total } = bucketize({ 'Some Unnamed Field': 5, 'Wilderness': 2 })
+  const wilderness = rows.find((r) => r.id === 'wilderness')
+  assert.equal(wilderness.count, 7)
+  assert.equal(total, 7)
+  // The reconciliation guarantee: the buckets sum to the total, exactly.
+  assert.equal(rows.reduce((s, r) => s + r.count, 0), total)
+})
+
+test('bucketize returns rows in BUCKETS order and drops empty buckets', () => {
+  const { rows } = bucketize({ 'Despise': 1, 'Britain': 1 })
+  assert.deepEqual(rows.map((r) => r.id), ['britain', 'dungeons']) // BUCKETS order, no empty towns/housing/wilderness
+})
+
+test('bucketize coerces non-numeric counts and tolerates empty/nullish input', () => {
+  assert.deepEqual(bucketize({}), { rows: [], total: 0 })
+  assert.deepEqual(bucketize(), { rows: [], total: 0 })
+  const { total } = bucketize({ 'Britain': '3', 'Minoc': 'oops' })
+  assert.equal(total, 3) // '3' → 3, 'oops' → 0
+})
+
+test('the last bucket is the catch-all (its match accepts anything)', () => {
+  const last = BUCKETS[BUCKETS.length - 1]
+  assert.equal(last.id, 'wilderness')
+  assert.equal(last.match('literally anything'), true)
+})