Add tea 0.10.1 nix derivation and Gitea PR skill

- Pin tea CLI to 0.10.1 to avoid TTY bug in 0.11.x
- Add .claude/skills/gitea for PR creation workflow
- Document tea CLI usage in CLAUDE.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nix/tea.nix

@@ -0,0 +1,53 @@
+{
+  lib,
+  stdenv,
+  fetchurl,
+}:
+
+let
+  version = "0.10.1";
+
+  sources = {
+    x86_64-linux = {
+      url = "https://dl.gitea.com/tea/${version}/tea-${version}-linux-amd64";
+      sha256 = "sha256-QcODwFm2T8hVCqBkp8FAnQ3KbNw8P0ZHv0iJ4zSP5mA=";
+    };
+    aarch64-linux = {
+      url = "https://dl.gitea.com/tea/${version}/tea-${version}-linux-arm64";
+      sha256 = "sha256-qfvJ4FJSHt1+sMG4hPwGNFLChqhNNf+l3ELQ97zZm50=";
+    };
+    x86_64-darwin = {
+      url = "https://dl.gitea.com/tea/${version}/tea-${version}-darwin-amd64";
+      sha256 = "sha256-WKjZKhFKWjZqnrdxPv00fzTIc0z4xrLSsL+jqLQ1huc=";
+    };
+    aarch64-darwin = {
+      url = "https://dl.gitea.com/tea/${version}/tea-${version}-darwin-arm64";
+      sha256 = "sha256-SMwxMEDKmhbLvLn1ZR1MmbjutZPk0P9QAfvNKCvrSk0=";
+    };
+  };
+
+  src = sources.${stdenv.hostPlatform.system} or (throw "Unsupported system: ${stdenv.hostPlatform.system}");
+in
+stdenv.mkDerivation {
+  pname = "tea";
+  inherit version;
+
+  src = fetchurl {
+    inherit (src) url sha256;
+  };
+
+  dontUnpack = true;
+
+  installPhase = ''
+    runHook preInstall
+    install -D $src $out/bin/tea
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "A command line tool to interact with Gitea servers";
+    homepage = "https://gitea.com/gitea/tea";
+    license = licenses.mit;
+    platforms = builtins.attrNames sources;
+  };
+}