docs: 重写 README

internal/updater/doc.go

@@ -26,10 +26,9 @@
 //     verified 2026-07-05) so Felis's UA is load-bearing there; PaperMC does NOT
 //     enforce (a bare request got HTTP 200 on 2026-07-04) so its UA is only etiquette.
 //     Also: felis-api's topology coord is now the real repository slug, not a placeholder,
-//     so that component resolves at runtime like the others — but only with a credential.
-//     The repo is private, so an unauthenticated poll gets GitHub's 404-for-hidden-repo and
-//     degrades to "latest unknown"; FELIS_GITHUB_TOKEN is what lights it up. k3s and
-//     cloudflared are public and need none.
+//     so that component resolves at runtime like the others, unauthenticated. A private
+//     fork answers an unauthenticated poll with GitHub's 404-for-hidden-repo and degrades
+//     to "latest unknown"; FELIS_GITHUB_TOKEN is what lights it up there.
 //
 //   - ALSO BUILT + UNIT-VERIFIED: the VersionGatherer's extraction core and dispatch.
 //     Three pure extractors turn raw system text into a Version — a `--version` banner