fix: prevent island names from shadowing JavaScript globals

[fry69]

fix #3521

Generated PR message below

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Problem

Island files named after JavaScript global objects (e.g., Map.tsx, Set.tsx, Promise.tsx) cause runtime errors. When UniqueNamer generates identifiers from these filenames, the resulting variable names shadow global constructors, breaking instantiation:

import Map from "/islands/Map.tsx";
boot({Map}, props);  // Map resolves to global constructor, not the island

This results in TypeError: Map is not a constructor when the framework attempts to use new Map() internally.

Solution

Added JavaScript global objects to the JS_RESERVED set in UniqueNamer. Names matching reserved keywords or globals are now automatically prefixed with underscore:

import _Map_1 from "/islands/Map.tsx";
boot({_Map_1}, props);  // No shadowing

Changes

• utils.ts: Extended JS_RESERVED with:

  • JavaScript built-ins (Map, Set, Array, Promise, Object, etc.)
  • Web APIs (fetch, console, URL, WebSocket, etc.)
  • Deno-specific globals (Deno namespace)
  • Node.js compatibility globals (process, Buffer, global)

• Integration tests: Added test cases for both Builder and Vite build systems verifying islands named after globals work correctly

Impact

Single-location fix in UniqueNamer applies to all code generation (islands, routes, etc.). Island names are prefixed when needed, preserving debuggability while preventing shadowing bugs.

[marvinhagemeister]

LGTM, thanks!