refactor(#2012): docs in own derivation, ship via claude --add-dir (no ~/.claude clobber)

nix/reference-docs.nix

@@ -0,0 +1,43 @@
+{
+  stdenv,
+  lib,
+}:
+
+# The repo `docs/` markdown tree, shipped as a standalone derivation so
+# agents can read the reference docs in-container (added as a claude
+# additional directory by the harness) WITHOUT pulling the branding +
+# prompt assets they don't need, and so the `hyperhive/website` repo can
+# reuse the exact same tree as a flake input.
+#
+# Pure data: the docs are copied verbatim (never transformed), so there
+# is no writable/build step — `$out` is the docs tree as-is.
+#
+# Output layout:
+#   $out/  — the repo `docs/` tree verbatim (e.g. `$out/setup.md`)
+
+stdenv.mkDerivation {
+  pname = "hyperhive-docs";
+  version = "0.1.0";
+  # Narrow src (just docs/) keeps this derivation's input hash decoupled
+  # from the rest of the tree — a doc edit only re-hashes this.
+  src = ../docs;
+
+  # No build: pure markdown, nothing to compile or render.
+  dontBuild = true;
+  dontConfigure = true;
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out
+    cp -r ./* $out/
+    runHook postInstall
+  '';
+
+  dontFixup = true;
+
+  meta = {
+    description = "hyperhive reference docs (the repo docs/ tree)";
+    homepage = "https://forge.darkest.space/hyperhive/hyperhive";
+    license = lib.licenses.mit;
+  };
+}