chore(playground): bump main chunk size limit 1750 → 1800 KB (#23107)

## Summary

Fix CI failure on `merge-train/fairies` (run
[25572561023](https://github.com/AztecProtocol/aztec-packages/actions/runs/25572561023),
log [1778264338812903](http://ci.aztec-labs.com/1778264338812903)).

The merge of `next` into `merge-train/fairies` (78632af) brought in
barretenberg changes — `feat!: optimized Poseidon2 (#22652)` and `feat:
n1 apps (#22974)` via `feat: merge-train/barretenberg (#23025)` — which
grew bb.js by enough to push the playground main entrypoint 0.02 KB over
the 1750 KB hard limit:

```
❌ assets/index-BEz4wQVA.js: 1750.02 KB exceeds limit of 1750 KB (Main entrypoint, hard limit)
```

Bumping the limit to 1800 KB (matching the prior +50 KB increment from
the bump log) restores headroom.

## Test plan

- [ ] CI green on this PR (chunk size check passes)


ClaudeBox log: https://claudebox.work/s/22af49d0486fc035?run=1

Author: AztecBot

playground/vite.config.ts

@@ -136,9 +136,10 @@ export default defineConfig(({ mode }) => {
         // Bump log:
         // - AD: bumped from 1600 => 1680 as we now have a 20kb msgpack lib in bb.js and other logic got us 50kb higher, adding some wiggle room.
         // - MW: bumped from 1700 => 1750 after adding the noble curves pkg to foundation required for blob batching calculations.
+        // - 2026-05-08: bumped from 1750 => 1800 after merge of next into merge-train/fairies brought in barretenberg changes (optimized Poseidon2, n1 apps) that nudged bb.js over the prior limit (1750.02 KB).
         {
           pattern: /assets\/index-.*\.js$/,
-          maxSizeKB: 1750,
+          maxSizeKB: 1800,
           description: 'Main entrypoint, hard limit',
         },
         // Bump log: