[ascandone]

What

Adds a browser WebAssembly build of numscript, so a host can parse, run and
statically analyse scripts entirely client-side — no backend.

Changes

• internal/wasmbinding — host-testable core (Check, Run,
  NeededVariables, Version) wrapping analysis.CheckSource and the
  interpreter over an in-memory StaticStore, emitting stable JSON envelopes.
  Diagnostics carry 0-based, LSP-aligned ranges/severities; balance amounts keep
  integer precision via big.Int; panics are recovered into error envelopes.
• cmd/wasm — a thin syscall/js shim (js && wasm build tag) that
  registers globalThis.__numscript.{check,run,getNeededVariables,version} and
  keeps the runtime alive.
• Justfile — just wasm builds dist/numscript.wasm + wasm_exec.js
  (standard Go, -ldflags="-s -w"; ~7.3 MB, ~1.7 MB gzip).

Why

Powers a fully client-side numscript playground (and any other editor):
real-time parse/type diagnostics with exact line spans, plus execution, without
a server round-trip.

Testing

• go test ./internal/wasmbinding/... (incl. -race), go vet (host + GOOS=js GOARCH=wasm), gofmt.
• Node smoke test of the built wasm: check (valid → none; invalid → error at the exact range), run (postings, 10^21 balance exact, missing-funds error), getNeededVariables.

https://claude.ai/code/session_016gu5cG7jeqGumbny3XkfDC

[NumaryBot]

🟡 [minor] Fixed-precision float fallback can silently change balance amounts

The fallback rounds the input to 256 bits before checking f.Int's accuracy. That accuracy only describes conversion of the already-rounded float, not preservation of the input. For example, a decimal balance consisting of 1 followed by a decimal point, 100 zeros and 1 rounds to exactly 1 and is accepted, contrary to the documented rejection of fractional amounts. Large scientific-notation integers beyond 256 significant bits can likewise be changed before execution.

Suggestion: Parse decimal/scientific notation exactly using an integer mantissa and decimal exponent (or an exact rational), and accept only values with no fractional remainder. Add tests for a fractional value smaller than the float precision and a scientific-notation integer exceeding 256 bits.

[NumaryBot]

🟡 [minor] Successful variable discovery omits the empty variables object

For a script with no required variables, NeededVariables initializes an empty map, but the variables,omitempty tag removes it from the response. The result is {"ok":true}, rather than the shim's documented successful {ok, variables} envelope. Hosts that enumerate the successful response's variables without a special missing-field fallback will fail for ordinary scripts with no inputs; the existing test only covers a nonempty map.

Suggestion: Keep variables present on successful responses, including an empty object, while retaining the error envelope shape as needed. Add a regression test asserting the raw JSON shape for a script with no required variables.