test: fix CI test isolation - upgrade Bun, fix mock contamination and fresh-import patterns

.github/workflows/ci.yml

@@ -37,11 +37,9 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      # Pin to 1.3.10: bun 1.3.11 breaks spyOn on ESM barrel re-exports,
-      # causing 7 createBuiltinAgents tests to fail in batch execution.
       - uses: oven-sh/setup-bun@v2
         with:
-          bun-version: "1.3.10"
+          bun-version: "1.3.11"
 
       - name: Install dependencies
         run: bun install
@@ -58,7 +56,7 @@ jobs:
 
       - uses: oven-sh/setup-bun@v2
         with:
-          bun-version: "1.3.10"
+          bun-version: "1.3.11"
 
       - name: Install dependencies
         run: bun install
@@ -83,7 +81,7 @@ jobs:
 
       - uses: oven-sh/setup-bun@v2
         with:
-          bun-version: "1.3.10"
+          bun-version: "1.3.11"
 
       - name: Install dependencies
         run: bun install