fix(npx): route unknown tools through npx instead of npm

[gghez]

Summary

• rtk npx <unknown-tool> was dispatching to npm instead of npx because the
  catch-all in the Npx match arm delegated to npm_cmd::run(), which hardcodes
  resolved_command("npm")
• Replaced the catch-all with a direct npx invocation that still applies npm
  boilerplate filtering via filter_npm_output

Test plan

• cargo fmt --all && cargo clippy --all-targets && cargo test
• 3 new tests covering npx argument parsing
• Manual testing: rtk npx cowsay hello output inspected

Fixes #815

[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

[gghez]

Thanks for the heads up — rebased and updated the import paths to crate::core::*. All tests passing.