v0.13.4

chore(release): 0.13.4 with combinator-free MCP tool schemas

Model providers restrict schema combinators in tool parameters:
Anthropic rejects oneOf, anyOf and allOf at the top level of a tool and
fails the whole request with a 400, and strict modes reject them
anywhere. schemars derived them in the MCP tools from Option<Struct>
fields, the untagged command and message-content enums and the tagged
AttentionResponse.

- AndaBrainMcpServer::new flattens each tool's schema: an optional
  struct field is its struct, alternatives of distinct types become one
  schema with a type list, and tagged variants become one object whose
  kind is an enum, with variant-only fields optional and named per kind
  in the description. Deserialization still checks the arguments.
- A test keeps every MCP tool free of combinators, and AGENTS.md records
  the rule for model-facing schemas.
- Lockfile refresh: anda_engine 0.16.7, anda_core 0.16.3,
  anda_cognitive_nexus 0.14.4, anda_db 0.14.2, anda_kip 0.14.1 and
  rmcp 3.5.1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>