docs: tighten the gt guides and the cli wiring

The workflow example had no trigger, so Gitea would reject it as written.
The guides now merge the small account sections and point users at the
nightly builds they describe. Comments and READMEs no longer mention the
dropped reference generator or list the runner as the only hand written
sidebar product, and the sidebar lookup drops a key the fallback covers.

Co-Authored-By: Claude (Opus 5.5) <[email protected]>

cli-docs/index.md

@@ -10,7 +10,7 @@ with repositories, issues, pull requests, releases, Actions and the other resour
 Gitea instance, from a terminal or a script.
 
 :::info Development version
-These pages describe builds from the `main` branch of gitea/cli.
+These pages describe builds from the `main` branch, published as `nightly` binaries and images.
 :::
 
 gt needs Gitea 28 or later, and Git for the commands that clone, check out or push.
@@ -34,6 +34,5 @@ gt needs Gitea 28 or later, and Git for the commands that clone, check out or pu
 
 `gt doctor` checks your setup and suggests a fix for each problem it finds.
 
-Every command documents itself with `--help`. `gt help environment`, `gt help formatting`
-and `gt help exit-codes` cover global flags and environment variables, JSON output, and
-exit codes.
+`gt <command> --help` lists the flags of a command, and `gt help environment` the global
+flags and environment variables.