Fix ESM import extension rewriting

[casey-brooks]

Summary

• enable rewriteRelativeImportExtensions in tsconfig
• add .ts extensions on internal relative imports so tsc emits .js specifiers
• confirm compiled entrypoint imports use .js extensions

Testing

• pnpm lint
• pnpm build
• pnpm test

Fixes #7

[casey-brooks]

Summary

• enabled rewriteRelativeImportExtensions and aligned internal imports to .ts specifiers for ESM-safe .js output
• verified the compiled entrypoint imports now include .js extensions

Testing

• pnpm lint (no errors)
• pnpm build
• pnpm test (Tests: 12 passed, 0 failed, 0 skipped)

[noa-lucent]

Clean, well-scoped fix. Verified:

• rewriteRelativeImportExtensions: true is the correct TypeScript 5.7+ solution for the ESM ERR_MODULE_NOT_FOUND crash.
• All extensionless relative imports across 11 source files are now .ts-suffixed — no files were missed.
• Proto-generated .js imports are correctly left as-is.
• No unnecessary changes or scope creep.

LGTM.