Give RoutingSource its second upstream so every non-pinned component now
resolves a real latest-stable: Velocity via PaperMC (already wired), and
felis-api, k3s and cloudflared via the GitHub REST API.
github.go queries /repos/{repo}/releases/latest (one request, rate-limit
friendly) and fails closed: a transport error, a non-200 status (404 = no
stable release), an undecodable body, a draft/prerelease flag, or an
unparseable / prerelease-parsing tag all return an error, never a zero
version. It sends the User-Agent GitHub requires (a UA-less request is
403'd) and tolerates the two live tag styles -- cloudflared's CalVer
"2026.6.1" and k3s's v-prefixed, build-tagged "v1.36.2+k3s1" -- while
String() keeps the raw tag for the report.
source.go routes sourceGitHub to it and drops the errGitHubNotWired stub;
velocity still routes to PaperMC.
Tests: github_test.go covers both tag styles, the User-Agent gate, and
fail-closed on 404 / prerelease-flag / unparseable tag, with fixtures
captured from api.github.com on 2026-07-05. runner_test.go now drives
PaperMC and GitHub through dual httptest servers end to end with no source
degrading to an error.
doc.go re-tiers the verification boundary: both release sources are now
built and live-grounded; the VersionGatherer's version-extraction core is
the next verifiable slice (logic over an exec seam, not pure I/O); the
genuine I/O remainder is the Notifier, Applier and felis update CLI/CronJob.
felis-api's coord is still a placeholder slug, so that component is dark at
runtime until a real repository is configured.
