Enable bounded runtime identity for chat

[RobLe3]

Summary

• make bounded runtime identity automatic for compatible chat and proxy chat surfaces
• retain disabled, explicit and required controls
• recompose candidate facts from original messages for sequential fallback
• preserve raw submit, Ollama raw generate and non-chat payloads
• avoid falsely labelling concurrent redundancy candidates as fallback

Validation

• full suite: 1175 passed, 2 skipped on Python 3.11, 3.12 and 3.13
• Ruff and mypy baseline passed
• coverage: 75.839%, minimum 75%
• dependency audit, locked build and clean wheel install passed
• canonical fixture parity passed

Closes #101
Depends on RobLe3/IICP#179.