Add UTF-8-safe base64 encoding for code blocks

[MarceloRGonc]

Part of OPS-4569.

Additional Notes

Code blocks running in the V8 isolate get a pure-JS base64 polyfill (btoa/atob). Those built-ins are Latin1-only and throw the string to be encoded contains characters outside of the Latin1 range whenever the input contains non-Latin1 characters (accented text, currency symbols, CJK, emoji), so any block that base64-encodes user data fails on such input.

This PR:

• Adds UTF-8-safe btoaUtf8/atobUtf8 helpers to the base64 polyfill that is bootstrapped into every code-block isolate. They are additive and behind typeof guards — existing btoa/atob behavior is unchanged.
• Ships ambient type declarations for the new helpers. Code blocks are type-checked with tsc before they run in the isolate, so without a declaration tsc rejects any block referencing the helpers with TS2304: Cannot find name 'btoaUtf8'. The declarations live next to the runtime polyfill (BASE64_POLYFILL_TYPES) and are written as openops-globals.d.ts into each block's compile directory by the code builder, keeping runtime and types in sync.

Testing Checklist

Check all that apply:

• I tested the feature thoroughly, including edge cases

• I verified all affected areas still work as expected

• Automated tests were added/updated if necessary

• Changes are backwards compatible with any existing data, otherwise a migration script is provided

Testing notes

• Added isolate round-trip tests in v8-isolate-code-sandbox.test.ts covering btoaUtf8/atobUtf8 encode, decode, a unicode round-trip (Coût € — 日本語 🚀), and a JSON.parse(atobUtf8(...)) decode of an encoded payload.
• Verified the compile-time fix with a standalone tsc --build: a block calling btoaUtf8 compiles with openops-globals.d.ts present and fails with TS2304 without it.
• npx nx lint engine and npx nx test engine pass.

[linear]

OPS-4569

[Copilot]

Pull request overview

Adds UTF-8-safe Base64 helpers to the engine’s V8 isolate bootstrap so code blocks can Base64-encode/decode arbitrary Unicode strings (not just Latin1), and ensures code blocks type-check cleanly by emitting matching ambient type declarations during compilation.

Changes:

• Extend the isolate base64 polyfill with btoaUtf8 / atobUtf8 (guarded, additive).
• Emit openops-globals.d.ts into each code-block compile directory so tsc recognizes the new globals.
• Add isolate-level tests validating UTF-8 encode/decode and round-trips for Unicode data.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/engine/test/core/code/v8-isolate-code-sandbox.test.ts	Adds coverage for UTF-8 base64 helpers in the isolate sandbox.
packages/engine/src/lib/core/code/polyfills/base64-polyfill.ts	Introduces btoaUtf8/atobUtf8 runtime polyfills and keeps their ambient type declarations alongside the polyfill.
packages/engine/src/lib/code-block/code-builder.ts	Writes openops-globals.d.ts during code-block compilation so tsc accepts the new globals.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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