[Schema] Stop rejecting elicitation schemas the specification allows

[chr-hertel]

The specification makes title optional on every elicitation schema definition. AbstractSchemaDefinition required it, so a client reading a conformant server's elicitation/create refused the request — and a server building one could not omit it either.

title is now nullable on all seven definitions, omitted from the serialized form when absent, and rejected only when present and not a string.

[Copilot]

Pull request overview

Updates the SDK’s elicitation schema definitions to align with the specification by making title optional across all supported schema types, ensuring conformant server payloads can be parsed and that serialization omits title when absent.

Changes:

• Make title nullable across all seven elicitation schema definition classes and adjust fromArray() to accept missing title.
• Update serialization to omit title when it’s null (notably via AbstractSchemaDefinition::buildBaseJson() and a custom update in EnumSchemaDefinition).
• Refresh unit tests to cover “missing title is accepted” and “non-string title is rejected”, and document the change in the changelog.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/Unit/Schema/Elicitation/TitledMultiSelectEnumSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/TitledEnumSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/StringSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/NumberSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/MultiSelectEnumSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/EnumSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
tests/Unit/Schema/Elicitation/BooleanSchemaDefinitionTest.php	Adds coverage for missing title being accepted and non-string title being rejected.
src/Schema/Elicitation/TitledMultiSelectEnumSchemaDefinition.php	Makes title nullable and optional in fromArray() for titled multi-select enums.
src/Schema/Elicitation/TitledEnumSchemaDefinition.php	Makes title nullable and optional in fromArray() for titled enums.
src/Schema/Elicitation/StringSchemaDefinition.php	Makes title nullable/optional and relies on base JSON builder to omit absent title.
src/Schema/Elicitation/NumberSchemaDefinition.php	Makes title nullable/optional and relies on base JSON builder to omit absent title.
src/Schema/Elicitation/MultiSelectEnumSchemaDefinition.php	Makes title nullable/optional and relies on base JSON builder to omit absent title.
src/Schema/Elicitation/EnumSchemaDefinition.php	Makes title nullable/optional and updates custom jsonSerialize() to omit absent title.
src/Schema/Elicitation/BooleanSchemaDefinition.php	Makes title nullable/optional and relies on base JSON builder to omit absent title.
src/Schema/Elicitation/AbstractSchemaDefinition.php	Centralizes “optional title” behavior in validation and base JSON building.
CHANGELOG.md	Documents the fix and its impact on interoperability with conformant servers.

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[chr-hertel]

Fixed in 3546d94 — updated to @param ?string $title Optional human-readable title for the field.

[chr-hertel]

Fixed in 3546d94 — updated to @param ?string $title Optional human-readable title for the field.

[chr-hertel]

Follow-up: c933262 adds the missing = null default to NumberSchemaDefinition's $title param — it was mistakenly grouped with the classes where a required param follows $title, but all of Number's subsequent params already have defaults, so it could safely take one too.