docs(skills): document URL install across features, reference, guide, and hermes-agent skill (#16355)

Follow-up to #16323 — the UrlSource adapter is shipped but four
user-facing docs surfaces still only listed the hub-identifier forms.

- user-guide/features/skills.md: add ``url`` to the Supported-hub-sources
  table; add a new "#### 8. Direct URL (`url`)" section explaining scope
  (single-file SKILL.md only), name-resolution order (frontmatter → URL
  slug → interactive prompt → --name flag), and both TTY and
  non-interactive usage. Add two URL examples to the install-examples
  block near the top of the page.
- reference/cli-commands.md: two URL install examples + one note
  explaining the name-resolution fallback chain.
- guides/work-with-skills.md: one URL-install example alongside the
  existing hub-identifier examples.
- skills/autonomous-ai-agents/hermes-agent/SKILL.md: Quick Reference
  block's ``hermes skills install`` line now spells out that ID can be
  a hub identifier OR a direct SKILL.md URL, and mentions --name for
  frontmatter-less skills.

No code changes. No new dependencies. Website builds via the usual
Docusaurus pipeline.

Co-authored-by: teknium1 <teknium@noreply.github.com>

website/docs/reference/cli-commands.md

@@ -617,6 +617,8 @@ hermes skills inspect official/security/1password
 hermes skills inspect skills-sh/vercel-labs/json-render/json-render-react
 hermes skills install official/migration/openclaw-migration
 hermes skills install skills-sh/anthropics/skills/pdf --force
+hermes skills install https://sharethis.chat/SKILL.md                     # Direct URL (single-file SKILL.md)
+hermes skills install https://example.com/SKILL.md --name my-skill        # Override name when frontmatter has none
 hermes skills check
 hermes skills update
 hermes skills config
@@ -627,6 +629,7 @@ Notes:
 - `--force` does not override a `dangerous` scan verdict.
 - `--source skills-sh` searches the public `skills.sh` directory.
 - `--source well-known` lets you point Hermes at a site exposing `/.well-known/skills/index.json`.
+- Passing an `http(s)://…/*.md` URL installs a single-file SKILL.md directly. When frontmatter has no `name:` and the URL slug isn't a valid identifier, an interactive terminal prompts for a name; non-interactive surfaces (`/skills install` inside the TUI, gateway platforms) require `--name <x>` instead.
 
 ## `hermes honcho`