docs(stovepipe): propose request history API

[mnoah1]

Summary

Intent:

• Expose the retained Stovepipe request log as public request history using SubmitQueue-aligned API terminology and response shapes.
• Keep current-state reads owned by operational entities instead of introducing a competing materialized projection.

Changes:

• Return ordered HistoryEvent values directly from request-ID lookup.
• Return repeated RequestHistory values from URI lookup; each contains only the request ID and ordered events, while the current mapping yields one and the contract can represent future retained attempts.
• Resolve URI, build strategy, and base URI from the Request instead of duplicating them in history responses.
• Define the direct projection from stored RequestLog records and explain why Stovepipe does not need SubmitQueue separate history materialization.
• Keep the raw request-log metadata map and validation degree out of the initial public API; a typed projection can be added when metadata readers and enforcement land.

This PR builds on the request-log RFC in #633.

Test Plan

• ./tool/bazel test //api/stovepipe/... //service/stovepipe/... //stovepipe/...
• make lint check-tidy check-gazelle

Revert Plan

Revert this documentation-only PR; #633 remains independently reviewable.

Jira Issues

None.