feat!: capabilities for tasks, elicitation

[devcrocod]

closes #544

Motivation and Context

How Has This Been Tested?

Breaking Changes

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

[Copilot]

Pull request overview

This PR updates the Kotlin MCP SDK capability model to add first-class tasks capabilities and to make elicitation capabilities structured/typed (rather than an opaque JsonObject), along with updating client/server strict-capability assertions and related tests.

Changes:

• Add typed ClientCapabilities.Elicitation (form/url sub-capabilities) and introduce ClientCapabilities.Tasks / ServerCapabilities.Tasks.
• Enforce tasks capability checks for tasks/* requests and notifications/tasks/status in Client and ServerSession.
• Update DSL/tests and API surface snapshots to reflect the new typed capability shapes.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
kotlin-sdk-server/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/server/ServerSessionAssertCapabilityTest.kt	Adds tests covering server-side capability assertions for tasks methods/notifications.
kotlin-sdk-server/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/ServerSession.kt	Adds tasks capability enforcement for outgoing tasks/* requests and notifications/tasks/status.
kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/types/dsl/InitializeDslTest.kt	Updates DSL tests to use typed elicitation capabilities.
kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/types/dsl/CapabilitiesDslTest.kt	Updates capabilities DSL tests for typed elicitation.
kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/types/CapabilitiesTest.kt	Expands serialization/deserialization coverage for tasks + typed elicitation.
kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/capabilities.kt	Introduces typed elicitation + tasks capability models (client/server) and deprecation bridge.
kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types/capabilities.dsl.kt	Updates DSL to accept typed elicitation (but currently lacks tasks support).
kotlin-sdk-core/api/kotlin-sdk-core.api	Updates public API snapshot for new capability types and signature changes.
kotlin-sdk-client/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/ClientAssertCapabilityTest.kt	Adds tests covering client-side capability assertions for tasks methods/notifications.
kotlin-sdk-client/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/client/Client.kt	Adds tasks capability enforcement for outgoing tasks/* requests and notifications/tasks/status.
integration-test/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/client/ClientTest.kt	Updates integration tests to use typed elicitation.

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[Copilot]

ClientCapabilities now has a tasks capability, but the DSL builder doesn’t expose any way to set it (and build() never populates it). This means users of buildInitializeRequest { capabilities { ... } } cannot declare task support via the DSL. Consider adding a private var tasks: ClientCapabilities.Tasks?, a fun tasks(value: ClientCapabilities.Tasks) setter, and wiring it into build() (and updating the builder KDoc list accordingly).

[Copilot]

Tasks methods were added to assertCapabilityForMethod, but assertRequestHandlerCapability still has no gating for tasks/* handlers. Since tasks requests can be received by either side, this allows registering handlers for tasks/get|result|list|cancel without advertising ClientCapabilities.tasks (and without checking list/cancel sub-capabilities). Consider adding corresponding tasks/* cases in assertRequestHandlerCapability that validate capabilities.tasks and, for list/cancel, capabilities.tasks.list/capabilities.tasks.cancel.

[Copilot]

Tasks methods were added to assertCapabilityForMethod (remote capability check), but assertRequestHandlerCapability still doesn’t enforce ServerCapabilities.tasks when registering local handlers for tasks/* requests. Since tasks requests are bidirectional, this can result in the server handling tasks/get|result|list|cancel without advertising tasks support (and without checking list/cancel sub-capabilities). Consider adding tasks/* cases to assertRequestHandlerCapability that validate serverCapabilities.tasks and the relevant sub-capability fields for list/cancel.