Add MCP elicitation support to TUI

Implement full MCP elicitation support in the runtime and TUI,
distinguishing between OAuth flows and standard elicitation requests.

- Add ElicitationDialog component that parses JSON schema to create
  form fields (string, boolean, integer, number, enum types)
- Add ElicitationResponseMsg to communicate responses from dialog
- Update handleElicitationRequest to route OAuth vs form elicitation
- Handle ElicitationResponseMsg in TUI to call ResumeElicitation

The elicitation dialog supports keyboard navigation, required field
validation, and proper type conversion for submitted values.

Assisted-By: cagent

Author: dgageot

examples/elicitation/.gitignore

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+__pycache__/*

examples/elicitation/README.md

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+# Elicitation Testing Example
+
+This example demonstrates how MCP (Model Context Protocol) elicitation works in cagent.
+Elicitation allows MCP tools to request additional input from the user during tool execution.
+
+## What is Elicitation?
+
+Elicitation is an MCP feature that enables tools to interactively prompt users for information
+that wasn't provided in the initial tool call. For example:
+- Asking for confirmation before destructive actions
+- Requesting missing required parameters
+- Gathering additional details when needed
+
+## Files in this Example
+
+- `agent.yaml` - The agent configuration that uses the elicitation MCP server
+- `server.py` - A Python MCP server that demonstrates various elicitation patterns
+- `README.md` - This documentation
+
+## Prerequisites
+
+You need `uvx` (part of [uv](https://docs.astral.sh/uv/)) installed:
+
+```bash
+# Install uv (includes uvx)
+curl -LsSf https://astral.sh/uv/install.sh | sh
+```
+
+The MCP SDK will be automatically installed when the server starts via `uvx`.
+
+## Running the Example
+
+```bash
+# From the cagent root directory
+./bin/cagent run examples/elicitation/agent.yaml
+```
+
+## Elicitation Scenarios
+
+The example MCP server provides several tools that demonstrate different elicitation patterns:
+
+### 1. Simple Confirmation (`confirm_action`)
+Shows a basic yes/no confirmation dialog before performing an action.
+
+**Example prompt:** "Confirm that I want to delete the database"
+
+### 2. Form Input (`create_user`)
+Demonstrates a multi-field form with validation:
+- Required string fields (username, email, role)
+- Optional fields (bio)
+- Email format validation
+- Enum/choice fields (role selection)
+- Boolean fields (active status)
+
+**Example prompt:** "Create a new user"
+
+### 3. Numeric Input (`configure_settings`)
+Shows number fields with min/max validation. Supports presets.
+
+**Example prompt:** "Configure settings with performance preset"
+
+### 4. Boolean Toggles (`setup_preferences`)
+Demonstrates multiple boolean fields with default values.
+
+**Example prompt:** "Set up my preferences"
+
+### 5. Enum Selection (`select_option`)
+Shows multiple enum/dropdown fields for making selections.
+
+**Example prompt:** "Help me select deployment options"
+
+## How Elicitation Works
+
+1. Agent decides to call an MCP tool
+2. Tool execution starts
+3. Tool sends an elicitation request with a message and JSON schema
+4. cagent displays an interactive dialog based on the schema
+5. User fills in the form and submits (or cancels)
+6. Response is sent back to the tool
+7. Tool continues execution with the provided data
+
+## Schema Field Types Supported
+
+- `string` - Text input (with optional format: email, uri, date, etc.)
+- `integer` - Whole number input
+- `number` - Decimal number input
+- `boolean` - Yes/No toggle
+- `enum` - Choice from predefined options (via `enum` array in schema)
+
+## Validation Options
+
+Fields can include validation constraints:
+- `required` - Field must be filled (specified at schema level)
+- `minLength`/`maxLength` - String length constraints
+- `minimum`/`maximum` - Number range constraints
+- `pattern` - Regex pattern matching
+- `format` - Built-in formats (email, uri, date)
+- `default` - Default value for the field
+
+## Testing the Server Standalone
+
+You can test the MCP server directly:
+
+```bash
+# Test initialization
+echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}' | \
+  uvx --with "mcp[cli]" python examples/elicitation/server.py
+```
+
+## Dialog Navigation
+
+When an elicitation dialog appears in the TUI:
+- **↑/↓** or **Tab/Shift+Tab** - Navigate between fields
+- **Space** - Toggle boolean fields
+- **Y/N** - Set boolean to Yes/No
+- **Enter** - Submit the form
+- **Esc** - Cancel the elicitation