Add v2 chat MCP support and expand v2 API parity

[FelixWaweru]

Summary

• add a new code-fundi-chat-v2 MCP tool backed by POST /v2/chat with robust JSON/NDJSON/text normalization
• add resilient fallback from v2 chat to legacy v1 chat for deployments that do not expose /v2/chat
• expand endpoint parity and schemas across existing tools/types:
  • fields now supports basic|summary|full|raw and custom path strings
  • stats tools now accept flexible Nd ranges (e.g. 1d, 60d, 365d)
  • auth tools now support idempotency/fingerprint/password-header request options
• add formatV2ChatResult formatter and update docs to include the new v2 chat tool

Validation

• npm run typecheck
• npm test
• npm run build