Wrap T3 Code apps with optional agent CLI paths

- Split base desktop/server derivations from wrapper layers
- Add optional PATH injection for codex, claudeCode, and opencode
- Update flake inputs and lock entries for nixpkgs/llm-agents

packages/t3code-server/default.nix

@@ -2,6 +2,7 @@
   lib,
   src,
   stdenv,
+  symlinkJoin,
   bun,
   codex ? null,
   claudeCode ? null,
@@ -28,11 +29,7 @@
 
   pname = "t3code-server";
   version = serverPackageJson.version;
-in
-  assert lib.assertMsg (!withCodex || codex != null) "withCodex requires a codex package";
-  assert lib.assertMsg (!withClaudeCode || claudeCode != null) "withClaudeCode requires a claudeCode package";
-  assert lib.assertMsg (!withOpencode || opencode != null) "withOpencode requires an opencode package";
-  stdenv.mkDerivation (finalAttrs: {
+  basePackage = stdenv.mkDerivation (finalAttrs: {
     inherit pname version;
     inherit src;
 
@@ -116,13 +113,6 @@ in
       cp -R --no-preserve=mode packages/shared "$out/libexec/t3code/packages/"
 
       makeWrapper ${lib.getExe nodejs} "$out/bin/t3" \
-        ${lib.optionalString withCodex ''
-          --prefix PATH : "${lib.makeBinPath [ codex ]}" \
-        ''}${lib.optionalString withClaudeCode ''
-          --prefix PATH : "${lib.makeBinPath [ claudeCode ]}" \
-        ''}${lib.optionalString withOpencode ''
-          --prefix PATH : "${lib.makeBinPath [ opencode ]}" \
-        ''} \
         --add-flags "$out/libexec/t3code/apps/server/dist/bin.mjs"
 
       runHook postInstall
@@ -136,4 +126,28 @@ in
       platforms = lib.platforms.unix;
       sourceProvenance = with lib.sourceTypes; [fromSource];
     };
-  })
+  });
+  withAgentPath = withCodex || withClaudeCode || withOpencode;
+  agentPath = lib.makeBinPath (
+    lib.optionals withCodex [codex]
+    ++ lib.optionals withClaudeCode [claudeCode]
+    ++ lib.optionals withOpencode [opencode]
+  );
+in
+  assert lib.assertMsg (!withCodex || codex != null) "withCodex requires a codex package";
+  assert lib.assertMsg (!withClaudeCode || claudeCode != null) "withClaudeCode requires a claudeCode package";
+  assert lib.assertMsg (!withOpencode || opencode != null) "withOpencode requires an opencode package";
+    if withAgentPath
+    then
+      symlinkJoin {
+        inherit pname version;
+        name = "${pname}-${version}";
+        paths = [basePackage];
+        nativeBuildInputs = [makeBinaryWrapper];
+        postBuild = ''
+          wrapProgram "$out/bin/t3" \
+            --prefix PATH : "${agentPath}"
+        '';
+        meta = basePackage.meta;
+      }
+    else basePackage