feat(parser): add WebAssembly support

[rabii-chaarani]

Summary

• add built-in WebAssembly Text support for .wat files under the webassembly language key
• vendor and compile the pinned ABI-15 tree-sitter-wat grammar with license, hashes, and offline package provenance
• normalize named modules, functions, types, imports, exports, and direct calls into the existing ontology while keeping anonymous constructs syntax-only
• expose WebAssembly through CLI and MCP syntax catalogs, dry-run discovery, README guidance, and k-wiki

Verification

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --locked -- -D warnings
• cargo test --workspace --locked
• cargo publish --dry-run --locked
• cargo run -p xtask -- verify-crate-size target/package/tmp-crate/codebase-graph-1.5.2.crate (9,837,470 bytes)
• k-wiki recommended validation, link checks, and site build

[rabii-chaarani]

Superseded by #107, which now combines WebAssembly Text with CSS, HTML, JavaScript/JSX, and TypeScript/TSX in one fully verified PR.