Replace nwnsc subprocess with WASM compiler for diagnostics

[PhilippeChab]

Summary

PR #62's intent was to migrate from spawning the native nwnsc binary
to the in-process Beamdog nwn_script_comp. This PR accomplishes that
goal but uses a WebAssembly build of the compiler instead, removing
the need for any native subprocess at all.

The WASM build comes from a fork of neverwinter.nim extended with
multi-error recovery, no-entry-point validation, and a clean C API
suitable for Emscripten.

Why WASM over the native binary

• Multi-error per pass. Reports every diagnostic in the file plus
  its #include'd helpers in a single compile, instead of stopping at
  the first error.
• Include validation works without a void main. Helper / include
  scripts can be edited and validated as the user types.
• One artifact, every platform. ~210KB WASM works anywhere Node
  runs. No separate Linux/Mac/Windows binaries to ship, no platform
  detection, no shell: true / powershell.exe quirks.
• In-process. No spawn / stdout parsing, no per-keystroke
  process startup overhead.

What changed

• server/wasm/nwscript_compiler.{js,wasm} — replaced with the new
  WASM build (~210KB, was ~308KB).
• server/src/Providers/DiagnosticsProvider.ts — rewritten:
  • Loads the WASM once on first publish.
  • Per publish, creates a compiler instance, sets
    collect-all-errors and require-entry-point=false, runs compile,
    drains the captured-error vector.
  • Resolver callback consults a per-call cache then asks the
    workspace file system for any name the compiler requests, so
    nwscript.nss and #included files are picked up automatically.
  • Errors that fire inside an include get routed to that include's
    own URI when we can resolve it, so the squiggle lands on the file
    that actually contains the bug.
  • Pre-seeds empty diagnostic lists for the target plus all
    transitive includes, so fixing an error clears the squiggle
    immediately.
• Removed: spawn(child_process) machinery,
  getExecutablePath / hasSupportedOS, nwnsc flag construction
  (-y -c -l -r -h -n -i), the line-by-line stdout parser.
• Kept (no-op for backwards compat with existing settings.json):
  compiler.os, compiler.nwnHome, compiler.nwnInstallation,
  compiler.reportWarnings.

What's left in place for safety

• server/resources/compiler/{linux,mac,windows}/nwnsc* — the native
  binaries are no longer referenced but kept on the branch so this
  PR can be reverted cleanly if the WASM approach hits a snag.

Once the WASM approach is verified in the wild, those ~13MB of
binaries can be deleted in a follow-up.

Test plan

• yarn compile:server passes (verified locally).
• yarn buildServer produces a working bundle (verified locally).
• Open a workspace with a broken .nss, confirm squiggles appear.
• Verify multi-error diagnostics: a file with three type errors
  on three separate lines should show three squiggles in one pass.
• Verify include validation: editing a helper file (no void main)
  produces diagnostics directly, no longer requires the file to be
  imported by a main script.
• Verify per-include error routing: an error in lib.nss reached
  via #include "lib" from main.nss shows on lib.nss.
• Verify clean state: fixing an error clears the squiggle.

🤖 Generated with Claude Code

[PhilippeChab]

Replaced by a clean PR from a branch off main. The original branch was based on top of an unrelated AST-tokenization commit, dragging that whole change into the diff.