[mnoah1]

Why?

Expose context already retained with Stovepipe history occurrences.

What?

• Add typed event payloads for build IDs on request-state, build-triggered, build-finished, and build-analysis-abandoned occurrences; validation degree on validation-fact-recorded; and project-fact count on project-facts-recorded.
• Omit payloads when metadata is unavailable or malformed, preserving valid zero values. Regenerate Go and TypeScript bindings.
• Read existing metadata only; no SQL changes or new event writers. Independent of the history-milestones PR.

Test Plan

Passed mapper, handler, and server tests; TypeScript generation and host type checks; and formatting, lint, tidy, and Gazelle checks.