initial: pi config — agents, prompts, skills, settings

Captures:
- 12 agent definitions (vigilio + a-team + utility)
- 8 mission prompt configurations
- 3 skills (forgejo, senior-software-engineer, xai-docs)
- pi settings.json (default provider/model)

.pi/agent/settings.json

@@ -0,0 +1,8 @@
+{
+  "lastChangelogVersion": "0.64.0",
+  "defaultProvider": "anthropic",
+  "defaultModel": "claude-opus-4-6",
+  "packages": [],
+  "hideThinkingBlock": false,
+  "defaultThinkingLevel": "medium"
+}