feat(nlp2dsl): constrain live conversation fields

[tom-sapletta-com]

Summary

• add a versioned ConversationFields contract bundle with GBNF, Protobuf, JSON Schema, and manifest
• request strict structured output and validate responses locally before merging fields
• reject fields outside the requested missing-field set
• use OpenRouter App identification with OPENROUTER_APP_NAME and project-folder fallback
• default the text boundary to openrouter/z-ai/glm-5.2

Validation

• full suite: 1679 passed, 17 skipped
• packaged wheel includes both TestQL contract bundles

Supersedes the automatically closed stacked PR #2 after its base branch was squash-merged and deleted.