Update DataCallback to Event-Based Structure

[spencerstock]

What changed? Why?

Updated DataCallback capability structure from flat request-based model to event-based architecture. The capability now supports three distinct event types: initiated, preSign, and postSign. Each event can include optional context data, and preSign events contain the data requests array (previously at root level).

Changes:

• Restructured DataCallbackCapability type to use events array instead of requests
• Added DataCallbackEvent type with type, context, and requests fields
• Updated code examples across datacallback.mdx, encodeProlink.mdx, and decodeProlink.mdx
• Documented event lifecycle hooks for better integration control

Notes to reviewers

The API surface changes from:

dataCallback: { requests: [...], callbackURL: "..." }

To:

dataCallback: {
  callbackURL: "...",
  events: [
    { type: 'initiated', context: {...} },
    { type: 'postSign', context: {...} }
  ]
}

How has it been tested?

Documentation changes validated through:

• Code examples updated to reflect new structure
• Type definitions validated for consistency
• Examples include proper event lifecycle usage

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1