refactor(oxfmt): Rewrite --init mode in JS

[leaysgur]

After giving it some thought, I decided to lean these features toward JS after all.

The reasons are:

• I want Rust side to focus on complex formatting tasks, while moving infrequently used commands elsewhere
• Code defining napi callbacks tends to become verbose

While --init itself worked on the Rust side, it will share some lines with upcoming --migrate, so I'm extracting this beforehand too.

Also, We were generating .jsonc, but I've switched to creating .json for now.

This is because running oxfmt immediately after generating .jsonc causes trailing comma diffs. 😨
I was hesitant to introduce a jsonc writer, so .json will enough for now.

[leaysgur]

• fix(oxfmt): Report exitCode correctly #16770
• refactor(oxfmt): Rewrite --init mode in JS #16769 👈 (View in Graphite)
• fix(oxfmt): Make Rust CLI as just formatting CLI #16768
• fix(oxfmt): Remove jsonc parser override for (j|t)sconfig(.*)?.json #16762
• main

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[charliecreates]

The biggest concern is Mode::Init => unreachable!(...) in the NAPI path, which can hard-crash the process if --init reaches Rust due to packaging/regression or direct invocation. The JS --init implementation is mostly fine, but $schema detection should match the previous Rust behavior (is_file) to avoid false positives. Consider tightening --init UX by rejecting extra arguments to prevent ambiguous behavior. Lint suppression for console is broader than necessary and should be scoped down.

Additional notes (2)

• Maintainability | apps/oxfmt/src-js/migration/init.ts:1-2
  The file disables no-console globally, which broadens the blast radius and makes it easy to accidentally introduce unrelated console usage later. Since this module has only a couple of logging lines, prefer narrowing the suppression to the specific lines or using a small logger wrapper that can be mocked in tests. (This is especially important for CLI code where stdout/stderr shape is part of the API.)

• Readability | apps/oxfmt/src/main_napi.rs:69-73
Mode::Init => unreachable!(...) will panic if JS ever fails to intercept --init (e.g., someone uses the NAPI entrypoint directly, or a packaging/regression causes the JS CLI to not run this path). Panicking turns a user-facing CLI error into a crash.

Given this mode still exists for help output, prefer returning a controlled non-zero result with a clear message. That preserves stability and makes failures diagnosable.

Summary of changes

Summary

JavaScript CLI

• Wrapped apps/oxfmt/src-js/cli.ts in an async IIFE and added a JS-side fast path for --init via runInit().
• Added apps/oxfmt/src-js/migration/init.ts implementing --init scaffolding for .oxfmtrc.json and optional $schema injection.

Rust CLI/NAPI surface

• Kept Mode::Init for help/arg parsing but changed behavior so Rust/NAPI treats it as unreachable (apps/oxfmt/src/main_napi.rs).
• Updated help text from .oxfmtrc.jsonc to .oxfmtrc.json (apps/oxfmt/src/cli/command.rs).
• Removed Rust init module (apps/oxfmt/src/init/mod.rs) and its exposure from apps/oxfmt/src/lib.rs.
• Simplified CLI exit code mapping by removing init-related variants (apps/oxfmt/src/cli/result.rs).

Tests

• Added apps/oxfmt/test/init.test.ts covering creation, $schema insertion, and abort behavior.
• Exported runCli and RunResult from apps/oxfmt/test/utils.ts for reuse.

[Boshen]

Merge activity

• Dec 12, 5:30 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Dec 12, 5:30 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Dec 12, 5:37 AM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #16768.
• Dec 12, 5:41 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Dec 12, 5:52 AM UTC: Merged by the Graphite merge queue.