fix(package): every entry point loads with require() - #29

🟢 Confidence 8/10 · likely safe to merge
Verified Node's condition matching and require(esm) on a synthetic export map; the CJS consumer's require("effect") line is the one thing I could not exercise here.
_{quality 100/100 · no findings · tests covered · risk high}

Adds a default condition beside import on all 12 export entries so CommonJS callers can require() the ESM entries, and extends the tarball check with a CommonJS consumer. Contained and safe to merge.

• All 12 exports entries gain default pointing at the same .mjs as import
• tests/package-consumer.cjs requires every entry from the installed export map
• check-package.ts runs the CommonJS consumer against the packed tarball
• README and getting-started document the Node 20.19+/22.12+ floor

_{5bb8bb2 · Updated on every push. Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}