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/authentication.md

@@ -38,20 +38,18 @@ token:
 gt auth login --host https://gitea.example.com --ssh-key ~/.ssh/id_ed25519
 ```
 
-## Where credentials are kept
+## Accounts
 
-Tokens go to the system keyring by default. `--credential-store file` keeps them in gt's
-configuration directory instead, for machines without a keyring. `gt auth status` lists
-your accounts and `gt auth logout` removes one.
+Tokens go to the system keyring, or with `--credential-store file` to gt's configuration
+directory on machines without one. Run `gt auth login` once per instance and account.
+gt picks the instance from the repository's remote or `--host`, and the account with
+`gt auth switch` or `--user`. `gt auth status` lists your accounts and `gt auth logout`
+removes one.
+
+For instances behind an access proxy, `--header` and `--client-cert` add headers and a
+client certificate.
 
 ## Git over HTTPS
 
 `gt auth setup-git` lets `git push` and `git fetch` over HTTPS use gt's login. gt's own
 clone and checkout commands need no setup.
-
-## Several instances and accounts
-
-Run `gt auth login` for each instance and account. gt picks the instance from the
-repository's remote or `--host`, and the account with `gt auth switch` or `--user`.
-For instances behind an access proxy, `--header` and `--client-cert` add headers and a
-client certificate; see `gt auth login --help`.