[codex] Document compatibility matrix

[samlaycock]

Summary

Documents the package compatibility and runtime support expectations requested by Issue #57.

• Adds a README compatibility table covering Bun installation, the effect peer dependency range, TypeScript support, ESM/CJS declarations, the fluent-effect/effect passthrough export, and Bun-based runtime validation assumptions.
• Adds the same focused support matrix to docs/package-exports.md, where entrypoint and import guarantees are already documented.
• Adds a patch changeset for the documentation update.

Impact

Consumers no longer need to infer package manager, peer dependency, module format, or entrypoint support from package.json, tsconfig.json, and package smoke tests.

Closes #57.

Validation

• bun fmt
• bun lint:fix
• bun test
• bun typecheck

[greptile-apps]

Greptile Summary

This PR adds a compatibility matrix to README.md and docs/package-exports.md covering package manager, effect peer dependency range (^3.21.0), TypeScript 5 support, ESM/CJS/declaration module formats, the fluent-effect/effect passthrough export, and Bun-based runtime assumptions. All documented values match what is declared in package.json.

• The README gains a new Compatibility section between the installation instructions and the Quick Start.
• docs/package-exports.md gains an equivalent Compatibility Matrix section with slightly more precise per-row wording suited to its entrypoint-focused audience.
• A patch changeset accompanies the update per the project's conventions.

Confidence Score: 5/5

Pure documentation change with no code modifications; all stated values are consistent with package.json.

The change adds two compatibility tables and a changeset file. Every factual claim in the tables (peer dependency range ^3.21.0, TypeScript 5, ESM/CJS exports, Bun-based tooling) is verified by package.json. There are no code paths touched.

No files require special attention.

Important Files Changed

Filename	Overview
.changeset/soft-ravens-dance.md	Patch changeset for the compatibility documentation additions.
README.md	Adds a Compatibility section with a six-row table covering package manager, Effect peer dependency, TypeScript, module formats, native Effect export, and runtime assumptions; all values match package.json.
docs/package-exports.md	Adds a matching Compatibility Matrix section; row wording is slightly more precise than the README equivalent (e.g. 'Root export' instead of 'Module formats') and consistent with the surrounding doc context.

_{Reviews (2): Last reviewed commit: "docs: clarify README package manager sup..." | Re-trigger Greptile}