feat(docs): phase 15 - the Rust group, its reference pages checked against their sources

PLAN.md §16 phase 15. A Rust group of fifteen pages after Ultima Online
(D70): the module, installing the bridge (installer, Pterodactyl egg, by
hand), connecting the site, verifying the bridge, linking Steam accounts,
permissions and groups, mod config, who sees who is online, events, zones
and rewards, optional plugins, the live map, troubleshooting, and three
reference pages - rust-link's sidecar.toml, the plugin's
RunicGateway.json, and the event kinds.

checkReference.mjs gains three Rust sections rather than a new check:
sidecar.toml keys and RUSTLINK_* overrides from Rust-Link config.rs,
RunicGateway.json from the plugin's PluginConfig, and the event kinds
in three classes against Module-Rust server/catalogue.js (D71). Every
admin screen was walked on the walk site before it was described (D36).

Core pages now hand off to the Rust group instead of linking out to the
docs repository. Three defects the re-read found here are fixed: the UO
/health sample's hard-coded protocol 4 (both games' samples now render
platform.json through <Code>), Authentication's missing Steam tab, and
two pages saying the site cannot reach EventsEnabled - false on Rust.

Installer v0.8.1 moved checkFacts red mid-phase; platform.json follows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

src/data/platform.json

@@ -26,7 +26,7 @@
     "the same way. Which game a repository belongs to is said once, under `games` below."
   ],
   "releases": {
-    "installer": "v0.8.0",
+    "installer": "v0.8.1",
     "Android-app": "v0.5.0",
     "link": "v2.3.0",
     "Module-uo": "v1.3.0",