docs: one help guide for agents (docs/reference/help.md, rig context get help) (#113)

* docs: point agents to the OpenRig help route when OpenRig misbehaves

Add a short pointer to https://www.openrig.dev/help/agents in the
managed start guidance every seat reads, the openrig-skills index (all
three identical copies, digests regenerated) and the README 'For agents'
line. The route sends a symptom to version-matched docs and known
issues and explains how to reach the team. rig --version and rig doctor
help when available, but a broken install is not a reason to skip the
page. No new command.

* docs: one help guide for agents, served by rig context get help

Agent help now lives in one file, docs/reference/help.md. It ships with every
install, so it matches the installed version, and Context7 indexes it. A new
static context pack, help, serves the same file through `rig context get help`
by symlinking to it. The pack build copies the link's target, so installs get a
real file.

The pack generator accepts a static-pack symlink only when it points to a file
under docs/reference/. Any other link fails the build before anything is
written. Tests cover the help pack's bytes and both symlink cases.

The startup guidance, the openrig-skills index (all three copies), the
onboarding capability map, README and SUPPORT now point to `rig context get
help`, falling back to the installed file or openrig.dev/help/agents (the same
text) when `rig` won't run.

* docs(help): say contact options, not a contact form

The website's help page lists email and public Q&A; it has no contact form.

* docs(help): load linked guides on demand; correct the installed fallback path

F1: `rig context get help` served help.md alone, so its links to
getting-started, instance-layout and rig-spec had nothing to resolve against.
A new static pack, reference, symlinks exactly those three files from
docs/reference/. help.md keeps its source-relative links and adds the
`rig context get reference/<file>[#section]` address beside each, so a guide
loads only when it's needed and a help read stays small.

F2: the broken-rig fallback named docs/reference/help.md "in the installed
package". The package build copies these files to daemon/docs/reference/ in
@openrig/cli. Corrected in help.md, the startup guidance and the openrig-skills
index (all three copies, digests regenerated).

Tests: the reference pack ships real files equal to their sources; every
address help.md teaches resolves through the daemon's address route, section
and whole-file; the help preview contains none of the three manuals; a fixture
proves the address check fails on a missing target; source links and the
installed-path text match build-package.sh.

---------

Co-authored-by: v-openrig-build <[email protected]>

.github/SUPPORT.md

@@ -3,6 +3,7 @@
 - **Docs:** https://openrig.dev/docs — getting started, CLI reference, configuration,
   troubleshooting. An index linking to agent-friendly documentation is at
   https://openrig.dev/llms.txt.
+- **Agents helping a user:** read [docs/reference/help.md](../docs/reference/help.md), or run `rig context get help`.
 - **Questions:** [Discussions › Q&A](https://github.com/mvschwarz/openrig/discussions/categories/q-a).
 - **Bugs:** [open an issue](https://github.com/mvschwarz/openrig/issues/new/choose) with the bug
   template. Include `rig --version`, your OS and Node versions, and relevant redacted command output.