fix(playground): bump main entrypoint chunk-size limit 1800 → 1850 KB (#23223)

## What

Bumps the hard chunk-size cap on the playground's main entrypoint chunk
(`assets/index-*.js`) in `playground/vite.config.ts` from **1800 KB →
1850 KB**, plus a bump-log entry.

## Why

The `merge-train/barretenberg` PR (#23137) is repeatedly failing in the
merge queue on a **deterministic** `yarn build` failure in
`playground/`:

```
❌ Chunk size validation failed:
  ❌ assets/index-Bc65D_YP.js: 1801.31 KB exceeds limit of 1800 KB (Main entrypoint, hard limit)
error during build: Error: Build failed: chunk size limits exceeded
```

(merge-queue log: `ci.aztec-labs.com/a34536031aaca0b9`)

The 1800 KB limit was only raised four days ago (#23107, 1750 → 1800).
The merge train bundles further bb-side changes on top of `next` —
notably `feat: multi-app kernel circuits (#23076)` — which nudged bb.js
~1.3 KB past the just-raised ceiling. It will fail on every queue
attempt until the cap is raised. 1850 KB restores a small amount of
headroom.

## Note

This lands the bump on `next`. To unblock #23137 immediately, `next`
needs to be re-merged into `merge-train/barretenberg` once this merges
(or the same one-liner can be applied directly on that branch — note
that branch's earlier conflict resolution dropped one of the two `=>
1800` bump-log comment lines, so expect a trivial conflict on the
comment block when re-merging).

No behavior change; CI build only.

---
*Created by
[claudebox](https://claudebox.work/v2/sessions/7ad309a3cd56537a) ·
group: `slackbot`*

Author: ledwards2225

playground/vite.config.ts

@@ -138,9 +138,10 @@ export default defineConfig(({ mode }) => {
         // - 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).
         // - JB: bumped from 1750 => 1800 after adding the `aztec_utl_getTxEffect` oracle handler, which pulls TxEffect / FlatPublicLogs / PrivateLog / PublicDataWrite into the eager PXE import path (#22979).
+        // - 2026-05-12: bumped from 1800 => 1850 after merge-train/barretenberg brought in further bb-side changes (multi-app kernel circuits #23076 etc.) that pushed the main entrypoint to 1801.31 KB, just over the limit raised four days earlier.
         {
           pattern: /assets\/index-.*\.js$/,
-          maxSizeKB: 1800,
+          maxSizeKB: 1850,
           description: 'Main entrypoint, hard limit',
         },
         // Bump log: