[Schema] Add CHANGELOG entry for the 2026-07-28 surface

Author: chr-hertel

CHANGELOG.md

@@ -16,6 +16,7 @@ All notable changes to `mcp/sdk` will be documented in this file.
 * Add sampling with tools support: sampling requests now accept tools and tool-choice preferences, messages support tool-use/tool-result content blocks and multiple content blocks, and clients can advertise the `sampling.context` and `sampling.tools` capabilities. Adds `ClientGateway::supportsSamplingTools()` / `supportsSamplingContext()` to check the sub-capabilities before sending, and `CreateSamplingMessageRequest::validateToolFlow()`, which asserts the spec's tool-flow rules across the whole message list — the client handler rejects a violating request with `-32602` instead of leaving it unanswered, and the gateway refuses to send one.
 * [BC Break] `SamplingMessage::$content` and `CreateSamplingMessageResult::$content` may now hold a list of content blocks instead of a single one, so code reading them directly must handle both. Use the new `getContentBlocks()` on either class to always get a list.
 * [BC Break] `CreateSamplingMessageResult` now rejects any role other than `assistant`, and rejects empty content, as the specification requires.
+* Add the remaining 2026-07-28 schema surface, all of it optional and defaulting to current behaviour: url-mode elicitation (`ElicitationMode`, `ElicitRequest::forUrl()`, `ClientGateway::elicitUrl()` and `supportsElicitationUrl()`), whose result carries the user's action alone — `ElicitResult::fromArray()` takes the request's mode and only requires content in form mode; the `elicitation.form` / `elicitation.url` sub-capabilities, where an `elicitation` capability naming no mode declares form, the only shape that existed before; `Icon::theme`; `Implementation::title`, now settable through `Client\Builder::setClientInfo()` and `Server\Builder::setServerInfo()`; `Tool::outputSchema` and `CallToolResult::structuredContent` widened to any JSON value, with `null` alone meaning absent; and the revision's three error codes (`-32020` header mismatch, `-32021` missing required client capability, `-32022` unsupported protocol version), the last of which `ProtocolVersionMiddleware` returns with the supported set as structured data the client can retry from.
 
 0.7.0
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