fix(ci): use Node 20 compatible Bun setup

Author: hyperpolymath

.github/workflows/ci.yml

@@ -57,7 +57,13 @@ jobs:
         with:
           node-version: "20"
       - name: Set up Bun
-        uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2
+        # v2.2.0 moved the action runtime to node24, which caused a workflow
+        # startup_failure before any job was instantiated on this runner path.
+        # Keep the setup action on its Node-20-compatible release until the
+        # runner accepts Node-24 actions; pin the installed Bun independently.
+        uses: oven-sh/setup-bun@735343b667d3e6f658f44d0eca948eb6282f2b76 # v2.0.2
+        with:
+          bun-version: "1.3.14"
       - name: Install dependencies
         run: opam install . --deps-only --with-test --with-doc --yes
       - name: Install tree-sitter CLI (for res-to-affine walker tests)