Compiler options for WASM builds

[maharshijinandra]

What is this

This PR adds support for custom compiler options in WASM mode.
Discussion: #598 (demo video in discussions thread)

Changes

• added support for compilerOptions in the WASM compile request/response flow
• validated compiler options on the backend against an allowlist
• included compiler options in the artifact cache key so different flags produce different cached builds
• cached compiler stderr alongside the wasm artifact, so compiler diagnostics remain available on cache hits
• added a Settings toggle compiler options
• improved output rendering logic to safely append when possible and reset only when the event stream diverges
• added tests wherever appropriate

How is this tested

• npx eslint .
• npx vitest run
• go test ./...
• UI tested on all screen sizes (mobile, laptop, iPad)