Docs: README and repo hygiene (2026-09-25 audit)

[pietechsolution]

Held for review. Please do not merge yet.

Changes

• README first paragraph now says what this package is (Python client for the SeatLayer API), followed by a short company line.
• README: every em dash rewritten as plain punctuation.
• RELEASE.md rewritten as a short, current guide. The old file was the first-publish checklist ("never been published", a repo that "does not exist yet"). The new one follows .github/workflows/release.yml (Trusted Publishing, tag push, version checks) and keeps the yank guidance.

Checks

• Docs only. No code or workflow changes.