perf(pokedex): send the box grid as packed rows with the page

The server load fetched a full combined-data page at a 9999 item page size,
carrying detail text and ownership fields the grid never renders, and the client
re-fetched the same payload after hydration.

Load a trimmed grid row instead and pack it as positional tuples so field names
are not repeated for every one of a thousand-plus entries. Entry detail is
fetched on demand from the new per-entry endpoint when a cell is opened, and the
grid marks itself interactive so other page-start work can queue behind it.

tests/unit/gridTransport.test.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect } from 'vitest';
+import { packGrid, unpackGrid, type PokedexGridRow } from '$lib/models/PokedexGridRow';
+describe('grid transport', () => {
+	it('round-trips missing catches and every flag combination', () => {
+		const rows: PokedexGridRow[] = Array.from({ length: 17 }, (_, flags) => ({
+			pokedexEntry: {
+				_id: String(flags),
+				pokedexNumber: 25,
+				pokemon: 'Pikachu',
+				form: 'Female',
+				spriteKey: '25',
+				canGigantamax: true
+			},
+			catchRecord:
+				flags === 16
+					? null
+					: {
+							_id: `catch-${flags}`,
+							caught: !!(flags & 1),
+							haveToEvolve: !!(flags & 2),
+							inHome: !!(flags & 4),
+							hasGigantamaxed: !!(flags & 8)
+						}
+		}));
+		expect(unpackGrid(packGrid(rows))).toEqual(rows);
+	});
+});