Add agentic workflow for automated soundness bug detection and reproduction (#8275)

* Initial plan

* Add soundness bug detector and reproducer agentic workflow

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Complete soundness bug detector workflow implementation

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

.github/workflows/soundness-bug-detector.md

@@ -0,0 +1,41 @@
+---
+description: Automatically validate and reproduce reported soundness bugs
+
+on:
+  issues:
+    types: [opened, labeled]
+  schedule: daily
+
+roles: all
+
+permissions: read-all
+
+network: defaults
+
+tools:
+  cache-memory: true
+  github:
+    toolsets: [default]
+  bash: [":*"]
+  web-fetch: {}
+
+safe-outputs:
+  add-comment:
+    max: 2
+  create-discussion:
+    title-prefix: "[Soundness] "
+    category: "Agentic Workflows"
+    close-older-discussions: true
+  missing-tool:
+    create-issue: true
+
+timeout-minutes: 30
+
+steps:
+  - name: Checkout repository
+    uses: actions/checkout@v5
+
+---
+
+<!-- Edit the file linked below to modify the agent without recompilation. Feel free to move the entire markdown body to that file. -->
+@./agentics/soundness-bug-detector.md