spec(scheduler-framework): finalize 4-level job-picker design

Redesign the plugin picker hierarchy to project→queue→job+preempt
(was 3-level). Adds LSF-style cross-queue preemption (SIGSTP) and a
unified v1/v2 dispatch loop. Requirements grow 6→9 to cover the new
preemption and cross-queue levels.

.kiro/specs/scheduler-framework/spec.json

@@ -0,0 +1,23 @@
+{
+  "feature_name": "scheduler-framework",
+  "created_at": "2026-07-09T21:20:00Z",
+  "updated_at": "2026-07-10T10:00:00Z",
+  "language": "en",
+  "phase": "requirements-generated",
+  "approvals": {
+    "requirements": {
+      "generated": true,
+      "approved": false
+    },
+    "design": {
+      "generated": false,
+      "approved": false
+    },
+    "tasks": {
+      "generated": false,
+      "approved": false
+    }
+  },
+  "ready_for_implementation": false,
+  "blocked_on": []
+}