feat(mcp): show MCP loading status before first response

[RealKai42]

This PR adds explicit MCP loading status events and surfaces them in both shell and web UIs so users see feedback while MCP tools are connecting.

• Add MCPLoadingBegin / MCPLoadingEnd wire events.
• Emit loading events in KimiSoul when MCP tool loading is pending.
• Add has_pending_mcp_tools() in KimiToolset to gate event emission.
• Handle new events in shell UI with a Connecting to MCP servers... spinner.
• Handle new events in web session stream with a temporary status message.
• Update ACP session matching and wire serde tests for new event types.

Checklist

• I have read the CONTRIBUTING document.
• I have linked the related issue, if any.
• I have added tests that prove my fix is effective or that my feature works.
• I have run make gen-changelog to update the changelog.
• I have run make gen-docs to update the user documentation.

---

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 5 additional findings.

[Copilot]

Pull request overview

This PR introduces explicit wire-level MCP loading lifecycle events and wires them through both CLI shell and web UIs so users get immediate feedback while MCP tools are connecting, before the first assistant response.

Changes:

• Add new wire event types MCPLoadingBegin / MCPLoadingEnd (Python + web TypeScript).
• Emit loading events in KimiSoul when MCP tool loading is still pending (using new KimiToolset.has_pending_mcp_tools()).
• Render MCP loading indicators in both the shell UI (spinner) and web session stream (temporary status message), and update ACP session matching + wire serde tests.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
web/src/hooks/wireTypes.ts	Adds TS wire event types and includes them in the WireEvent union.
web/src/hooks/useSessionStream.ts	Displays/removes a temporary “Connecting to MCP servers…” status message on MCP loading events.
tests/core/test_wire_message.py	Extends wire serde snapshot coverage to include the new MCP loading message types.
src/kimi_cli/wire/types.py	Defines MCPLoadingBegin/End models and includes them in the wire Event union + exports.
src/kimi_cli/ui/shell/visualize.py	Adds an MCP “connecting” spinner and prioritizes it in the live view compose order.
src/kimi_cli/soul/toolset.py	Adds has_pending_mcp_tools() helper to detect in-flight background MCP loading.
src/kimi_cli/soul/kimisoul.py	Emits MCPLoadingBegin/End around wait_for_mcp_tools() when MCP loading is pending.
src/kimi_cli/acp/session.py	Updates match handling to accept/ignore the new MCP loading messages.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.