fix: lazy-load @gsd/pi-tui in shared/ui.ts to prevent /exit crash (#1761)

The eager top-level import of @gsd/pi-tui in shared/ui.ts caused any
command that transitively loaded the shared/mod barrel (including /exit)
to fail when extensions were loaded from ~/.gsd/agent/extensions/ where
@gsd/pi-tui has no node_modules resolution path.

Replaced the static import with a lazy require() accessor that defers
resolution to the first makeUI() call, so modules that import shared/mod
for non-TUI exports (constants, format utils, etc.) no longer trigger
the unresolvable dependency.

Closes #1640

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/resources/extensions/gsd/tests/lazy-pi-tui-import.test.ts

@@ -0,0 +1,46 @@
+// Verifies that shared/ui.ts does NOT eagerly import @gsd/pi-tui at the
+// module level.  An eager top-level import causes /exit (and any other
+// command that transitively loads shared/mod → shared/ui) to blow up when
+// @gsd/pi-tui cannot be resolved — e.g. extensions copied to
+// ~/.gsd/agent/extensions/ where no node_modules tree exists.
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const uiSrc = readFileSync(join(__dirname, "../../shared/ui.ts"), "utf-8");
+
+test("shared/ui.ts has no top-level import from @gsd/pi-tui", () => {
+  // Match lines like: import { ... } from "@gsd/pi-tui";
+  // But ignore type-only imports (import type / import("@gsd/pi-tui").X)
+  // and comments.
+  const lines = uiSrc.split("\n");
+  for (const line of lines) {
+    const trimmed = line.trim();
+    // Skip comments and type-only references
+    if (trimmed.startsWith("//") || trimmed.startsWith("*") || trimmed.startsWith("/*")) continue;
+    // Skip type-only import statements
+    if (trimmed.startsWith("import type ")) continue;
+    // Skip inline import() type annotations (erased at runtime)
+    if (/import\(["']@gsd\/pi-tui["']\)/.test(trimmed) && !trimmed.startsWith("import ")) continue;
+
+    // Flag any eager import statement pulling runtime values from @gsd/pi-tui
+    if (/^\s*import\s+\{/.test(line) && line.includes("@gsd/pi-tui")) {
+      assert.fail(
+        `Found eager top-level import from @gsd/pi-tui — this must be lazy.\n` +
+          `Line: ${trimmed}`,
+      );
+    }
+  }
+});
+
+test("shared/ui.ts lazily resolves @gsd/pi-tui inside makeUI", () => {
+  // The lazy accessor pattern: require("@gsd/pi-tui") inside a function body
+  assert.ok(
+    uiSrc.includes('require("@gsd/pi-tui")'),
+    "Expected a lazy require(\"@gsd/pi-tui\") call inside a function body",
+  );
+});

src/resources/extensions/shared/ui.ts

@@ -29,7 +29,21 @@
  */
 
 import { type Theme } from "@gsd/pi-coding-agent";
-import { truncateToWidth, visibleWidth, wrapTextWithAnsi } from "@gsd/pi-tui";
+
+// ─── Lazy @gsd/pi-tui resolution ─────────────────────────────────────────────
+// Deferred to first makeUI() call so that importing this module (via the
+// shared/mod barrel) does not blow up when @gsd/pi-tui cannot be resolved —
+// e.g. for commands like /exit that never render TUI components.
+
+type PiTuiFns = typeof import("@gsd/pi-tui");
+let _piTui: PiTuiFns | undefined;
+function piTui(): PiTuiFns {
+	if (!_piTui) {
+		// eslint-disable-next-line @typescript-eslint/no-require-imports
+		_piTui = require("@gsd/pi-tui") as PiTuiFns;
+	}
+	return _piTui;
+}
 
 // ─── Glyphs ───────────────────────────────────────────────────────────────────
 // Change these to restyle every cursor, checkbox, and indicator at once.
@@ -201,6 +215,8 @@ export interface UI {
 export function makeUI(theme: Theme, width: number): UI {
 	// ── Internal helpers ───────────────────────────────────────────────────────
 
+	const { truncateToWidth, visibleWidth, wrapTextWithAnsi } = piTui();
+
 	const add = (s: string): string => truncateToWidth(s, width);
 	const wrap = (s: string): string[] => wrapTextWithAnsi(s, width);