fix: improve path resolution for npx and non-standard entry points

[QuantGeekDev]

Summary

• Updates BaseLoader.resolveDirectory() to walk up from process.argv[1] looking for tool/prompt/resource directories, handling npx's temp directory structure
• Adds null guard for process.argv[1] in the fallback path
• Preserves backward compatibility: explicit basePath and CWD dist/ checks still take priority

Test plan

• 3 new tests pass in tests/loaders/BaseLoader-path-resolution.test.ts
• Publish a test package and run via npx to verify tools are discovered
• Verify existing npm start workflows still work

Closes #82

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