fix(resolve): resolve project-local node_modules/.bin tools (fixes exit 127 for hook-rewritten npx on Windows)

[danscMax]

Problem

The agent Bash hook (rtk hook claude / cursor / gemini / copilot) rewrites npx <tool> to rtk <tool>, dropping the npx launcher. RTK then resolves the tool through resolve_binary → which::which, which only searches the system PATH.

Project-local JS tools — eslint, vite, vitest, tsc, prettier, playwright, … — are installed in ./node_modules/.bin, which is not on the system PATH. So on Windows:

$ rtk eslint --version
rtk: Failed to resolve 'eslint' via PATH, falling back to direct exec: Binary 'eslint' not found on PATH
[rtk: program not found]      # exit 127

…even though npx eslint --version runs fine. npx/npm add node_modules/.bin to PATH at runtime; RTK strips the launcher during the rewrite but never replicated that lookup. The result: every hook-rewritten npx <local-tool> invocation fails with exit 127 for locally-installed tooling — the common case, since running not-globally-installed tools is exactly what npx is for.

Fix

resolve_binary now mirrors npx's resolution order:

1. nearest node_modules/.bin (cwd walking up to the filesystem root — handles monorepos / nested packages)
2. then the inherited PATH

…via which::which_in (PATHEXT-aware on Windows; already used in this module's tests). tool_exists uses the same resolution so handlers that branch on it (tsc_cmd, next_cmd, prisma_cmd, …) also detect local tools.

• Native tools unaffected: git, cargo, npm, etc. aren't in node_modules/.bin, so they fall through to PATH exactly as before — this is an additive change to the search path.
• Bonus correctness: a project-local tool now takes precedence over a globally-installed shadow of the same name (e.g. a playwright on PATH from another ecosystem), matching npx semantics.

The logic is split into a testable resolve_binary_in(name, cwd, path_var) so resolution can be unit-tested without mutating global process state. Adds tests for local-node_modules/.bin resolution and the not-found path.

Verification (Windows 11)

command	before	after
rtk eslint --version	exit 127	v9.39.4, exit 0
rtk vite --version	exit 127	vite/6.4.3, exit 0
npx eslint --version (hook-rewritten → rtk eslint)	exit 127	exit 0
rtk git status / rtk npm run / rtk cargo --version	ok	ok (no regression)

cargo check is clean on develop; the resolution unit tests pass (cargo test resolve_binary).

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