hive-forge: add markdown-docs generator and CI freshness check

nix/checks.nix

@@ -241,4 +241,22 @@ in
     fi
     touch "$out"
   '';
+
+  # `hive-forge` CLI reference freshness check — same shape as
+  # `hivectl-docs` above, `hive-forge markdown-docs` (clap-markdown over
+  # its own command tree) instead. Reuses `packages.<system>.hive-forge`
+  # (already built as its own package, out of `daemonBins` — see
+  # nix/packages/default.nix's comment on it).
+  hive-forge-docs =
+    pkgs.runCommand "hive-forge-docs-fresh" { nativeBuildInputs = [ pkgs.diffutils ]; }
+      ''
+        ${self.packages.${system}.hive-forge}/bin/hive-forge markdown-docs > generated.md
+        if ! diff -u ${../docs/tools/forge-cli.md} generated.md; then
+          echo "" >&2
+          echo "ERROR: docs/tools/forge-cli.md is out of date — regenerate it:" >&2
+          echo "  nix build .#hive-forge && ./result/bin/hive-forge markdown-docs > docs/tools/forge-cli.md" >&2
+          exit 1
+        fi
+        touch "$out"
+      '';
 }