Expose browser language intelligence

[konojunya]

Summary

• expose compiler-owned completion and hover through the native Engine facade and typed browser WebAssembly package
• derive bounded completion entries from the effective core catalog and validated caller-owned provider packs
• preserve language-intelligence schema 1.0, UTF-8 ranges, plain-text documentation, and caller-owned document versions for stale-result suppression
• bump @stack-sh/engine to 0.7.0 and update only the Engine provenance in approved SVG snapshots
• add native/browser parity fixtures, TypeScript and capability checks, and explicit editor latency budgets

Verification

• cargo +stable test --workspace --locked
• formatter and Engine conformance suites against the pinned Specification
• exact renderer and seven-case layout snapshots
• release-mode language intelligence: 100 completion + hover pairs in 6.161 ms, 0.076 ms p95
• release-mode layout budget
• npm run build:wasm && npm test && npm run typecheck && npm run pack:check
• WebAssembly import and exported-operation audit
• native/WebAssembly completion, hover, multilingual position, provider catalog, and document-version parity
• cargo +stable clippy --workspace --all-targets --all-features --locked -- -D warnings
• cargo +1.85.0 test --workspace --locked
• cargo +1.85.0 clippy --workspace --all-targets --all-features --locked -- -D warnings
• RUSTDOCFLAGS="-D warnings" cargo +stable doc --workspace --no-deps --locked
• WASI/native geometry parity with Wasmtime 48.0.1
• cargo audit and npm audit --audit-level=moderate (0 vulnerabilities)
• LLVM coverage: 97.18% lines, 95.68% functions, 95.09% regions