PLAN.md currently ends at Phase 21, and all Phase 21 issues are closed. There are no open issues or pull requests to drive the next implementation iteration. Define the next phase before creating further implementation work.
Acceptance criteria:
- Add a Phase 22 section to PLAN.md with a clear goal and concrete scope.
- Phase 22 should be WebAssembly: parse, validate, and execute .wasm modules in pure Rust, with full JS API bindings (WebAssembly.Module, Instance, Memory, Table, Global, compile, instantiate, compileStreaming, instantiateStreaming).
- Cover the WebAssembly MVP plus widely-deployed post-MVP features (sign-extension, multi-value, reference types, bulk memory).
- Keep the scope aligned with the project constraints in CLAUDE.md: zero external crates, pure Rust subsystems, and unsafe only in the allowed crates (a new we-wasm crate must be 100% safe Rust; any AArch64 JIT work belongs in we-js).
- Include a test milestone: pass the WebAssembly spec test suite for the MVP, and run a real Rust-compiled wasm module end-to-end (fetch, instantiate, call exports from JS).
- Identify which existing test suites to extend (WPT for the JS API surface, Test262-style for spec conformance, e2e for end-to-end pages embedding wasm).
- Break the phase into enough bullet points that the next automation pass can verify all implementation issues line up.
- Do not implement Phase 22 features in this issue; this is roadmap definition only.