fix: measure a queued discard against the value it named, not a write count

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/lib/itemStore.svelte.ts

@@ -472,13 +472,15 @@ class Entry<V> {
 	}
 
 	discard(): Promise<DiscardOutcome> {
-		// What a discard throws away is the value as of the click, like a save sends the value as
-		// of the click: one typed while it waited its turn behind a save is newer than it, and
-		// reverting that would drop it with nothing left to recover it from.
-		const askedAt = this.edits
+		// What a discard throws away is the value as of the click, the way a save sends the value
+		// as of the click. One typed while it waited its turn is newer than the discard, and
+		// reverting it would drop it with nothing left holding it. Measured as the value and not
+		// as a count of writes: an outside write of what is already on screen changes nothing the
+		// user can see, so it does not make their discard stale.
+		const asked = serialize(this.value)
 		return this.run(async () => {
 			if (!this.loaded || this.retired) return { removed: false }
-			if (this.edits !== askedAt) return { removed: false }
+			if (serialize(this.value) !== asked) return { removed: false }
 			if (this.origin === 'draft') {
 				const kept = snapshot(this.value)
 				const keptRow = this.row

frontend/src/lib/itemStore.test.ts

@@ -519,6 +519,29 @@ describe('item store: origins', () => {
 		})
 	})
 
+	it('discards behind an outside write of the value already on screen', async () => {
+		const rows = fakeRows()
+		const gate = deferred()
+		const { item } = await open(
+			rows,
+			adapter({ deployed: deployedRes }, () => gate.promise)
+		)
+		item.value = { ...deployedRes, description: 'edited' }
+		const saving = item.save()
+		await settle()
+		const discarding = item.discard()
+		await settle()
+		// The chat saves what the user is already looking at: nothing on screen moves, so the
+		// discard is still about the value its click named.
+		item.applyExternal({ ...deployedRes, description: 'edited' })
+		gate.resolve()
+
+		expect(await saving).toMatchObject({ ok: true })
+		expect(await discarding).toEqual({ removed: false })
+		expect(item.dirty).toBe(false)
+		expect(rows.writes.at(-1)).toEqual({ path: 'u/me/r', value: null })
+	})
+
 	it('keeps a draft-only item an outside write put back while its delete was going', async () => {
 		const rows = fakeRows()
 		const draft = { ...deployedRes, description: 'only a draft' }