feat: split diffs language pack

Split the diffs viewer Shiki language pack into an external publishable plugin.

The diffs plugin keeps the default curated syntax set, while the new @openclaw/diffs-language-pack package carries the extended Shiki languages for npm and ClawHub distribution. The install metadata includes the external ClawHub spec, and the curated C# alias set keeps both c# and cs supported without the language pack.

Co-authored-by: Dallin Romney <dallinromney@gmail.com>

test/scripts/oxlint-config.test.ts

@@ -123,6 +123,7 @@ describe("oxlint config", () => {
     expect(ignorePatterns).toContain("**/.cache/**");
     expect(ignorePatterns).toContain("**/.openclaw-runtime-deps-copy-*/**");
     expect(ignorePatterns).toContain("extensions/diffs/assets/viewer-runtime.js");
+    expect(ignorePatterns).toContain("extensions/diffs-language-pack/assets/viewer-runtime.js");
   });
 
   it("enables strict empty object type lint with named single-extends interfaces allowed", () => {

test/scripts/runtime-postbuild.test.ts

@@ -39,6 +39,7 @@ describe("runtime postbuild static assets", () => {
       "dist/extensions/acpx/error-format.mjs",
       "dist/extensions/acpx/mcp-command-line.mjs",
       "dist/extensions/acpx/mcp-proxy.mjs",
+      "dist/extensions/diffs-language-pack/assets/viewer-runtime.js",
       "dist/extensions/diffs/assets/viewer-runtime.js",
     ]);
   });
@@ -59,8 +60,12 @@ describe("runtime postbuild static assets", () => {
       "dist/extensions/acpx/error-format.mjs",
       "dist/extensions/acpx/mcp-command-line.mjs",
       "dist/extensions/acpx/mcp-proxy.mjs",
+      "dist/extensions/diffs-language-pack/assets/viewer-runtime.js",
       "dist/extensions/diffs/assets/viewer-runtime.js",
     ]);
+    expect(payload.sources).toContain(
+      "extensions/diffs-language-pack/assets/viewer-runtime.js",
+    );
     expect(payload.sources).toContain("extensions/diffs/assets/viewer-runtime.js");
   });