fix: resolve CLI path for tier-check conformance subprocess

[DePasqualeOrg]

Problem

tier-check shells out to run conformance tests using a relative path:

execSync(`node dist/index.js server --url ${options.serverUrl} -o ${outputDir}`, {
  cwd: process.cwd(),
  ...
});

When invoked via npx (or from any directory other than the conformance package root), process.cwd() points to the user's working directory, not the package directory. dist/index.js doesn't exist there, so the command fails silently (the error is caught on the next line), the output directory is empty, and reconcileWithExpected counts every expected scenario as a failure — producing 0% conformance scores.

Fix

Replace node dist/index.js with node "${process.argv[1]}", which resolves to the absolute path of the currently running CLI entry point regardless of working directory. Also removes the now-unnecessary cwd: process.cwd().

Testing

Ran tier-check from /tmp against my Swift SDK's conformance server.

Related

PR #168 addresses a similar issue on Windows (single-quote quoting in execSync) but retains the relative dist/index.js path, so the npx problem would persist even after that fix.

Breaking Changes

None

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling (n.a.)
• I have added or updated documentation as needed (n.a.)