Implement SEP-1577 to enable tool calling in sampling requests.

Major changes:
- Add tools and toolChoice parameters to sampling/createMessage
- Introduce ToolUseContent and ToolResultContent message types
- Support parallel tool calls via content arrays
- Add sampling.tools and sampling.context capabilities to ClientCapabilities
- Soft-deprecate includeContext values thisServer/allServers

Breaking changes:
- Content fields can now be arrays (for parallel tool calls)
- Wire-level backward compatible
- Tool result messages cannot contain mixed content types

Updates:
- schema/draft/schema.ts: New types and updated interfaces
- schema/draft/schema.json: Auto-generated from TypeScript
- docs/specification/draft/schema.mdx: Auto-generated from TypeScript
- docs/specification/draft/client/sampling.mdx: Tool calling docs with examples
- docs/specification/draft/changelog.mdx: SEP-1577 entry

Cross-API compatibility:
- Compatible with Claude, OpenAI, and Gemini APIs
- Message content constraints ensure clean role mapping
- Tool IDs support APIs without native ID support

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Co-Authored-By: Claude <noreply@anthropic.com>

… message balance requirement

- Make ToolResultContent.content required (not optional) to align with CallToolResult
  per SEP Oct 27 update that states "aligned on CallToolResult"
- Add documentation for message balance requirement in sampling.mdx
  (tool use messages must be followed by corresponding tool results)
- Regenerate schema.json and schema.mdx from updated types

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Aligns terminology with existing naming:
- type: "tool_use"
- ToolUseContent
- stopReason: "toolUse"

Updated all documentation and comments to use "tool use" instead of
"tool calling" for feature name consistency.

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Co-Authored-By: Claude <noreply@anthropic.com>

Keep original 5 security considerations unchanged and add tool-specific
items (6-12) as new additions rather than rewriting all items.

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Co-Authored-By: Claude <noreply@anthropic.com>

- Remove redundant items (user approval already covered in item 1)
- Remove off-topic items (validation, sanitization, timeouts)
- Consolidate into key requirement: servers MUST respond to all tool uses
  and ensure tool result messages contain only tool results

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Co-Authored-By: Claude <noreply@anthropic.com>