spike(w012): harden in-process WASM analyzer M1

[1932819331hy-debug]

W-012 Milestone 1 — In-process WASM checker feasibility

This PR contributes a testable, AI-assisted feasibility spike for Issue #268 / wildcard W-012, accepted into the 2026-11-01 M1 review window. It embeds the existing Rust checker as wasm32-unknown-unknown in Go with Wazero, provides a real golang.org/x/tools/go/analysis.Analyzer, and publishes correctness, failure-boundary, and performance evidence. It does not claim a production replacement for hyb, stock gopls integration, or M2 completion.

Implemented and reviewed

• Build the existing Rust checker for WASM and call it from Go without a per-request external Rust process.
• Map on-disk sibling .hy diagnostics to Go source positions for go vet -vettool.
• Preserve accepted managed-safety warnings and distinguish user-code rejection from infrastructure failures; malformed envelopes, WASM traps, cancellations, and invalid memory bounds fail closed.
• Bound the public Engine.Check call, add cancellable CheckContext, and isolate concurrent analyzer context snapshots.
• Fail closed if a declared .hy input is unreadable; canonicalize file paths to avoid duplicated diagnostics, and report source files in deterministic order.
• Exercise parity, regressions, race safety, diagnostic positions, and infrastructure-failure cases in a repeatable hosted CI workflow.

Latest hosted verification

• Tested head: 1e6f2e22dcae2e7c90f6f3721ed7f0b58b7c3d17 (with its then-current PR merge base).
• [W012 validation workflow](https://github.com/limitlessprojects/Go-Hybrid/actions/runs/39169949673): 113/113 checker-corpus verdict agreement and 113/113 complete normalized native/WASM diagnostic-envelope parity; go test -race -count=1 ./... and go vet ./... succeeded.
• [Compiler CI](https://github.com/limitlessprojects/Go-Hybrid/actions/runs/39169949669): passed.
• The detailed [M1 review report](https://github.com/1932819331hy-debug/Go-Hybrid/blob/spike/w012-m1-hardened/W012_M1_REVIEW.md) and [reproducible measurement record](https://github.com/1932819331hy-debug/Go-Hybrid/blob/spike/w012-m1-hardened/spikes/w012-inprocess/validation-2026-10-18/README.md) distinguish current correctness evidence from earlier benchmarks and their raw samples.

Negative results and open limitations

• The measured public Engine.Check path was 2.143 ms p50 versus 1.204 ms p50 for native subprocess + JSON validation on the measured cloud host (one representative fixture, 100 samples). A reusable-instance experimental boundary measured 1.097 ms p50, but it is not the implemented public path. This does not validate the original 18.7× speedup or sub-millisecond IDE-latency claim. The later cancellation/path-hardening changes have not been rebenchmarked.
• Stock gopls cannot dynamically load arbitrary external analyzers or treat unsaved .hy buffers as first-class Go documents. The demonstrated go/analysis driver works with on-disk .hy files; a separate LSP/editor integration remains unimplemented.
• Go analysis.Diagnostic has no warning severity level, so go vet -vettool may exit nonzero for managed-warning-only files even though the native Hybrid checker accepts them.
• No 25-file/100-edit editor latency benchmark, long-duration memory soak, or final cross-platform packaging claim is made.

Reproduction

From the same checkout with Rust 1.99.0, Go 1.26.9, Node 24.19.0, and the wasm32-unknown-unknown target:

(cd compiler && cargo build --locked --release -p hyb)
(cd compiler && cargo build --locked --release -p hy-wasm --target wasm32-unknown-unknown)
export HYBRID_WASM_PATH="$PWD/compiler/target/wasm32-unknown-unknown/release/hy_wasm.wasm"
export HYBRID_NATIVE_PATH="$PWD/compiler/target/release/hyb"
node test_wasm_parity.js
(cd spikes/w012-analyzer && go test -race -count=1 ./... && go vet ./...)

Scope and disclosure: The proposal, implementation, and tests were developed with AI assistance. Hosted CI results above reflect actual completed runs; no unperformed personal manual verification is claimed. M1/M2 acceptance and compensation remain entirely at the maintainer's discretion.