[Madraka]

Step 1 of RFC-0041's rollout (ADR-0043). No behaviour change: nothing reads the new module yet.

Contract

• site.schema.json gains an optional CollectionSettings.fields (1–30 items).
• FieldDefinition is a oneOf of nine variants with discriminator type: text, richText, number, boolean, date, datetime, url, image, select. Labels, options and the migration marker are new $defs.
• content-entry.schema.json changes only the fields description.
• Fixtures: 2 valid (every type and option, plus a minimal one) and 28 invalid. TS and Rust are regenerated; Rust emits #[serde(tag = "type", deny_unknown_fields)] enum FieldDefinition.

@cloudhal/core-ts/fields (Worker-safe, eval-free, rule 6)

• checkFieldDefinitions and fieldDefinitionChanges: reserved keys, uniqueness, caps (30 per collection, 200 per site, 256 KB for collections), and the §6 guard (field_change_needs_operation).
• fieldsPropsSchema plus checkFieldValues: compiled to ADR-0030's props subset for validateProps, with per-type checks (date, datetime {at, timeZone}, URL schemes, asset id, select), changed-only checking, refusal of unknown keys, and the 256 KB cap.
• checkRequiredToPublish: for review and publish.
• fieldsJsonSchema: limited to what OpenAI and Anthropic strict modes accept, with a golden file.
• resolveFields: localized values fall back to the original's (fromOriginal); non-localized values come from the original.

Decisions where the RFC was ambiguous

• validateProps caps strings at 10,000 characters, so the 50,000 limit for richText is checked in code.
• Removing a key or option needs counting stored values, which fieldDefinitionChanges reports for step 2.
• The value conversion table is left to step 3.

Checks

• core-contracts: 478 tests.
• New field tests: 82.
• cargo test and clippy pass.
• Packaging, size check and no drift pass.

Changeset: minor, like RFC-0040 step 1, so this moves the fixed group to 0.5.0.

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