closes#544
Replaces opaque `JsonObject?` modelling of `elicitation` with a typed
`ClientCapabilities.Elicitation` (`form`, `url`), and adds the new
`tasks` capability on both `ClientCapabilities` and `ServerCapabilities`
(with `list`, `cancel`, per-request-type augmentation). Wires capability
assertions for `tasks/*` methods and `notifications/tasks/status` into
`Client` and `ServerSession`
## How Has This Been Tested?
unit tests
## Breaking Changes
yes
now elicitation is a specific class in capabilities
## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [x] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed
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