fix(frontend): add prism/r type shim so tsc unblocks Cloud Build

[MarkusNeusinger]

Why

The frontend changes from PR #6961 — languages count on the landing strip, ggplot2 card on /libraries, R code viewer on /scatter-basic/r/ggplot2 — are merged on main, but production still shows the pre-#6961 state:

$ curl -s https://anyplot.ai/assets/constants-Cv1rI8LA.js | head -c 200
…LIBRARIES=['altair','bokeh','highcharts',…]  # no ggplot2
$ curl -s https://anyplot.ai/assets/LandingPage-Bluw1eOY.js | grep -oE '.{20}languages.{20}'
…children:[{value:`1`,label:`languages`}…    # hardcoded '1'

All served assets carry last-modified: Sat, 16 May 2026 20:04:15 GMT — about 2.5 h before #6961 merged. The API was redeployed (/stats now returns "languages":2,"libraries":10), but the frontend Cloud Run revision is stale.

Root cause

The frontend Cloud Build (app/cloudbuild.yaml → yarn build = tsc && vite build) fails at the tsc step:

src/components/CodeHighlighter.tsx(3,15): error TS7016: Could not find a declaration
file for module 'react-syntax-highlighter/dist/esm/languages/prism/r'.
'…/react-syntax-highlighter/dist/esm/languages/prism/r.js' implicitly has an 'any' type.

@types/react-syntax-highlighter actually does ship an ambient declaration for this exact path (line 2768 of its index.d.ts), but with moduleResolution: "bundler" tsc resolves the import to the sibling .js file first and never reaches the @types index — only r trips, python from the line above happens to resolve through the cached package types. Net effect: tsc exits non-zero, vite build never runs, no new Docker layer, Cloud Run keeps serving the previous revision.

Docker build log confirmed this:

ERROR: build step 0 "gcr.io/cloud-builders/docker" failed: step exited with non-zero status: 2
The command '/bin/sh -c yarn build' returned a non-zero code: 2

PR #6961 listed this exact TS error under "Out of scope" — it had been latent since #6944 added the R import, and only became a deploy blocker because #6961 was the first frontend-touching PR after the lib bumps that affect tsc behavior.

Fix

Add app/src/types/react-syntax-highlighter.d.ts declaring the missing module locally. A project-local shim wins over @types, which is enough to unblock tsc. The runtime import is unchanged — Prism still registers the real R grammar via registerLanguage('r', r), and a grep over the rebuilt CodeHighlighter-*.js confirms the R keyword set is bundled:

break|else|for|function|if|in|next|repeat|while

So R syntax highlighting on /scatter-basic/r/ggplot2 works as intended.

Test plan

• cd app && yarn build — green (was failing on TS7016 before)
• cd app && yarn test — 459/459 green
• New bundle hash differs from the deployed one (LandingPage-e58y3raq.js vs prod LandingPage-Bluw1eOY.js), confirming the redeploy will publish fresh assets
• After merge: Cloud Build for anyplot-app finishes green; https://anyplot.ai/assets/LandingPage-*.js no longer contains the hardcoded {value:'1',label:'languages'}
• After deploy: landing strip shows languages: 2, /libraries shows the ggplot2 card, /scatter-basic/r/ggplot2 code panel renders R code with highlighting

Notes

• This PR does not re-introduce the language count / ggplot2 / R-code-viewer logic — those landed in fix(frontend+api): wire R/ggplot2 into code viewer, libraries page, languages count #6961 and are already on main. This only removes the build blocker so the existing fixes can actually reach production.
• The Cloud Build "deploy-app (anyplot) ✅ Passed" check that appeared on fix(frontend+api): wire R/ggplot2 into code viewer, libraries page, languages count #6961's merge commit was from .github/workflows/notify-deployment.yml, which is a no-op echo step that records a GitHub Deployment object — it does not actually report the GCP Cloud Build outcome. Worth a follow-up to either wire the real Cloud Build status back to the commit or rename the workflow so the green check doesn't mislead.

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