fix(bin): pass search params via env vars (RCE fix) (#819)

Replace shell string interpolation with process.env in gstack-learnings-search
to prevent arbitrary code execution via crafted learnings entries. Also fixes
the CROSS_PROJECT interpolation that the original PR missed.

Adds 3 regression tests verifying no shell interpolation remains in the bun -e block.

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

test/learnings-injection.test.ts

@@ -0,0 +1,48 @@
+import { describe, test, expect } from "bun:test";
+import { readFileSync } from "fs";
+import path from "path";
+
+const SCRIPT = path.join(import.meta.dir, "..", "bin", "gstack-learnings-search");
+
+describe("gstack-learnings-search injection prevention", () => {
+  const script = readFileSync(SCRIPT, "utf-8");
+
+  test("no shell interpolation inside bun -e string", () => {
+    // Extract the bun -e block (everything between `bun -e "` and the closing `"`)
+    const bunBlock = script.slice(script.indexOf('bun -e "'));
+
+    // Should NOT contain ${VAR} patterns (shell interpolation)
+    // These are RCE vectors: a malicious learnings entry with '; rm -rf / ;' in the
+    // query field would execute arbitrary commands via shell interpolation.
+    const shellInterpolations = bunBlock.match(/'\$\{[A-Z_]+\}'/g) || [];
+    const bareInterpolations = bunBlock.match(/\$\{[A-Z_]+\}/g) || [];
+
+    // Filter out any that are inside process.env references (those are safe)
+    const unsafeInterpolations = [
+      ...shellInterpolations,
+      ...bareInterpolations,
+    ].filter((m) => !m.includes("process.env"));
+
+    expect(unsafeInterpolations).toEqual([]);
+  });
+
+  test("uses process.env for all user-controlled values", () => {
+    const bunBlock = script.slice(script.indexOf('bun -e "'));
+
+    // Must use process.env for TYPE, QUERY, LIMIT, SLUG, CROSS_PROJECT
+    expect(bunBlock).toContain("process.env.GSTACK_SEARCH_TYPE");
+    expect(bunBlock).toContain("process.env.GSTACK_SEARCH_QUERY");
+    expect(bunBlock).toContain("process.env.GSTACK_SEARCH_LIMIT");
+    expect(bunBlock).toContain("process.env.GSTACK_SEARCH_SLUG");
+    expect(bunBlock).toContain("process.env.GSTACK_SEARCH_CROSS");
+  });
+
+  test("env vars are set on the bun command line", () => {
+    // The env vars must be passed to bun, not just set in the shell
+    expect(script).toContain("GSTACK_SEARCH_TYPE=");
+    expect(script).toContain("GSTACK_SEARCH_QUERY=");
+    expect(script).toContain("GSTACK_SEARCH_LIMIT=");
+    expect(script).toContain("GSTACK_SEARCH_SLUG=");
+    expect(script).toContain("GSTACK_SEARCH_CROSS=");
+  });
+});