docs(sourcehut-ci): fix factual errors found in full audit
Verified the skill against the actual upstream sources mirrored in this
workspace and fixed every concrete claim that didn't match the code:
- Secrets management URL is builds.sr.ht/secrets, not meta.sr.ht/secrets
(route lives in builds.sr.ht/buildsrht/blueprints/secrets.py; meta has
no /secret* route). Updated SKILL.md, manifest.md, secrets-and-oauth.md.
- SSH key secret installation path: the worker uses the manifest entry
verbatim, so name references land at ~/.ssh/<name>, not ~/.ssh/<uuid>
(builds.sr.ht/worker/tasks.go SendSecrets).
- ubuntu/lts now points to resolute (26.04 LTS); oldlts points to noble.
Added jammy and questing to the shipped-versions list.
- hut todo subcommands: rewrote the block to match v0.8.0 — `create` and
`comment` only accept --stdin (no -t/-s/-b), `update-status` (not
`update`), `list` reads --tracker (persistent flag on `hut todo`).
- hut pages acl update --id is required (MarkFlagRequired in
hut/pages.go), not optional.