feat(tui): port Fase 4 TUI logic layer — InputState/Action dispatcher/key controller/slash commands + lightweight ANSI renderer + run loop; 20 test

apps/interfaces/tui/src/git.ts

@@ -0,0 +1,26 @@
+/**
+ * Git diff preview helper — shells out to `git diff` over the workspace
+ * roots and returns the combined output text. Mirrors
+ * `apps/interfaces/tui/src/action/git.rs`.
+ */
+import { execSync } from "node:child_process";
+
+/** Run `git diff` across the given workspace roots and return the output. */
+export function gitDiffOutput(workspaceRoots: string[]): string {
+  for (const root of workspaceRoots) {
+    try {
+      const out = execSync("git diff --stat && git diff", {
+        cwd: root,
+        encoding: "utf8",
+        maxBuffer: 4 * 1024 * 1024,
+        stdio: ["ignore", "pipe", "ignore"],
+      });
+      if (out.trim().length > 0) {
+        return out;
+      }
+    } catch {
+      // Not a git repo or git not available — continue to the next root.
+    }
+  }
+  return "No diff available (not a git repository).";
+}