feat: add agent-mock package for deterministic E2E testing (#33)

New package @united-workforce/agent-mock (uwf-mock CLI):
- Reads pre-scripted outputs from a YAML mock data file (--mock-data)
- Counts existing CAS chain steps to determine step index
- Validates expected role matches actual moderator routing
- Stores minimal detail node in CAS for valid step refs
- Zero LLM, instant execution, 100% deterministic

Usage in config.yaml:
  agents:
    mock:
      command: uwf-mock
      args: ["--mock-data", "./fixtures/scenario.yaml"]

Refs #33

proman.yaml

@@ -23,6 +23,10 @@ packages:
     path: packages/agent-builtin
     type: cli
 
+  - name: "@united-workforce/agent-mock"
+    path: packages/agent-mock
+    type: cli
+
   - name: "@united-workforce/cli"
     path: packages/cli
     type: cli