Enable core chat orchestration to use Workspace Search, Analyze, and Compare

## Summary

Build Workspace document action orchestration into the core Semantic Kernel chat agent/action layer used by both streaming and non-streaming Chat.

Today, the Simple Chat action can search workspace knowledge, but it does not support Analyze or Compare, and it does not have intent-selection logic to decide whether a user request should use Search, Analyze, Compare, or normal Q&A.

This issue proposes making that orchestration a core Chat capability so:

- Normal Chat users can get better document reasoning without manually selecting an agent.
- Agents using assigned knowledge plus the Simple Chat action automatically gain the same Workspace-aware behavior.
- Workflows built on top of agents can also benefit from Search, Analyze, Compare, and clarifying-question behavior.

## User Value

Users currently need to understand the difference between Workspace mode, Analyze, Search, Compare, and normal Chat. That creates a multi-step flow and requires mode switching.

The improved experience should allow users to ask naturally, while the core chat agent determines whether it needs to search, analyze, compare, ask a clarifying question, or produce a final answer.

This also makes agents more powerful without requiring every agent to reimplement document-action logic separately.

## Proposed Behavior

- The core Semantic Kernel chat agent/action layer can use Workspace document actions.
- The same capability works in both streaming and non-streaming Chat.
- The Simple Chat action can invoke Search, Analyze, and Compare where appropriate.
- The chat agent can decide which action to use based on user intent:
- Search for targeted retrieval or fact finding.
- Analyze for deeper extraction, summarization, structured analysis, or report-building.
- Compare when the user asks about differences, similarities, gaps, conflicts, or tradeoffs between documents.
- General Q&A when no Workspace action is needed.
- The chat agent can ask clarifying questions before choosing an action when user intent is ambiguous.
- Clarifying questions can include structured chat UI inputs, such as buttons or selectable document choices.
- For Compare, the chat flow can ask which documents should be compared when the request does not clearly identify them.
- Agents with assigned knowledge and the Simple Chat action inherit this capability.
- Workflows using those agents can also use this capability.

## Acceptance Criteria

- [ ] Core Semantic Kernel chat orchestration supports Search, Analyze, and Compare over workspace documents.
- [ ] The behavior works in streaming Chat.
- [ ] The behavior works in non-streaming Chat.
- [ ] The Simple Chat action can invoke Analyze and Compare, not only Search.
- [ ] Intent-selection logic chooses Search, Analyze, Compare, or general Q&A based on the user request.
- [ ] The chat agent can ask clarifying questions when intent or document selection is ambiguous.
- [ ] Chat UI supports structured clarification inputs such as selectable buttons or document choices.
- [ ] Compare flow can request or infer which documents should be compared.
- [ ] Users can benefit from this behavior without selecting a custom agent.
- [ ] Agents using assigned knowledge plus the Simple Chat action inherit the same behavior.
- [ ] Workflows built on agents can use the same capability.
- [ ] Workspace document permissions and selected-document scoping are preserved.
- [ ] Functional tests cover streaming, non-streaming, agent, and workflow-relevant paths.

## Notes

This should not be implemented as a one-off Workspace Document Analysis Agent feature only.

The preferred direction is to make Workspace document action selection a core capability of the chat orchestration layer. A specialized agent can still be created later, but the base Chat experience and Simple Chat action should both gain the ability first.

Current gap:

- Simple Chat action supports Search.
- Simple Chat action does not support Analyze.
- Simple Chat action does not support Compare.
- Chat orchestration does not currently choose between Search, Analyze, Compare, and Q&A based on user intent.
- Chat UI may need new clarification controls for intent selection and document selection, especially for Compare.