Port JavaScript sources when their extensions are configured

[calvin-archastro]

Problem and intent

rustify only sees .ts/.tsx. Projects with plain JavaScript modules, such as astroshots, whose astroshot CLI is bin/*.mjs, can't track those files in the port, so the CLI would be ported outside the graph, index, and ratchet.

Goal: let a project opt JavaScript files into the graph and port them exactly like TypeScript.

What changed

• New extensions key in rustify.toml, default ["ts", "tsx"]. Existing configs behave as before.
• With js/mjs/cjs/jsx added:
  • discovery picks them up under roots (.d.ts and dist/ are still never sources)
  • they parse with the TypeScript grammar (.jsx uses TSX)
  • an import of ./x.mjs resolves to x.ts/x.tsx first, then x.mjs. Bare imports also try .js/.mjs/.cjs/.jsx and index.*. Candidates whose extension isn't configured are ignored.
  • they map to Rust files with the extension stripped: bin/cli.mjs becomes bin/cli.rs
• The UI golden checks also treat .jsx as a component.
• rustify graph | head no longer prints a broken-pipe panic.
• Docs: configuration.md, workflow.md, the README, and the example rustify.toml.

Scope: CLI only. Risk: low, because the default leaves current behavior unchanged. No user impact unless extensions is set.

Testing

• Canonical end-to-end test: tests/porting_workflow.rs::ports_javascript_modules_when_their_extensions_are_configured. It runs the real binary against a temporary git repository with a .mjs CLI that imports another .mjs file and a TS module:
  • with the default config, the graph is empty
  • with mjs configured, all three files are in the graph and the brief maps bin/cli.mjs to bin/cli.rs / cli::bin::cli
  • the .mjs test is found
  • start and done record the symbol map
• Unit test: packages::tests::a_javascript_import_falls_back_to_the_javascript_file_after_typescript, plus the existing candidate test, which now also asserts that dist/ never becomes a source.
• cargo test (21 unit + 16 e2e), clippy -D warnings, and fmt --check all pass locally. CI runs them in the rustify workflow on this PR.

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