docs: move docs to RunicGateway/docs, repoint all references

Extracted docs/ (ADMIN_CONTROLS, INTEGRATION, PLAN, PROTOCOL_2, RESEARCH,
SHARD_PREREQS) into the central RunicGateway/docs repo under link/, with
full commit history preserved via git filter-repo.

The source cites these design docs by section throughout, so every in-repo
reference (C# + Rust comments, Bridge.cfg, and the READMEs) is repointed at
the new docs-repo URL. README references are rendered as markdown links; a
Documentation pointer section is added to the top-level README.

Docs repo: https://gitea.whitlocktech.com/RunicGateway/docs

overlay/Scripts/Custom/Bridge/BridgeNews.cs

@@ -8,7 +8,7 @@ namespace Server.Custom.Bridge
 {
     /// <summary>
     ///     Website news articles pushed into the modern Town Cryer News gump
-    ///     (docs/PROTOCOL_2.md §16). Distinct from BridgeTownCrier, which drives the scrolling-crier
+    ///     (https://gitea.whitlocktech.com/RunicGateway/docs/src/branch/main/link/PROTOCOL_2.md §16). Distinct from BridgeTownCrier, which drives the scrolling-crier
     ///     announcement lines (GlobalTownCrierEntryList). Here the full article — title, body (HTML),
     ///     image, and a "more info" URL — becomes a TownCryerNewsEntry in TownCryerSystem.NewsEntries,
     ///     which the stock news gumps already render (they branch on TextDefinition.Number, so string