feat(chat): add AskQuestions mode for contextual clarification

[SeleiXi]

Description

This PR introduces an explicit Ask Questions mode. When enabled, it requires the model to first inspect the current request and conversation context, identify the most important missing information, and ask the user a focused set of clarification questions before completing the task.

Motivation

Users do not always know how to formulate a complete request. In many cases, they may know the outcome they want, but may not know:

• which details are important to provide;
• what assumptions the model is currently making;
• what context is still missing for a high-quality answer; or
• which constraints would materially affect the result.

Key changes

• Register the ask_questions mode across the runtime, CLI, and web capability picker.
• Add the ask CLI alias.
• Force ask_user on the first internal loop round while suppressing any pre-tool narration.
• Resume the same agent turn after single- or multi-question replies.
• Add localized English and Chinese questioning policies.
• Preserve resolved ask_user questions and answers in later-turn context.
• Support both SQLite and PocketBase session stores without introducing a new persistence schema.
• Add tests for capability registration, prompt localization, forced first-round tool selection, pause/resume behavior, CLI aliases, and context persistence.

Use Case & Screenshot

Related Issues

Closes #775

Module(s) Affected

• agents
• api
• config
• core
• knowledge
• logging
• services
• tools
• utils
• web (Frontend)
• docs (Documentation)
• scripts
• tests
• Other: ...

Checklist

• I have read and followed the contribution guidelines.
• My code follows the project's coding standards.
• I have run pre-commit run --all-files and fixed any issues.
• I have added relevant tests for my changes.
• I have updated the documentation (if necessary).
• My changes do not introduce any new security vulnerabilities.