Execution API: document RTIF endpoint

[Vamsi-klu]

Why

The Execution API spec lacks OpenAPI metadata for the RTIF endpoint, which makes client generation and discovery harder. This change documents the endpoint; runtime behavior is unchanged.

Tests

Not run (metadata-only change).

Follow-ups

• Validate map_index range when creating task instances via CLI #60463 Validate map_index range when creating task instances via CLI
• Improve executor callback log file template #60464 Improve executor callback log file template
• Remove ui_color/ui_fgcolor from SerializedBaseOperator #60465 Remove ui_color/ui_fgcolor from SerializedBaseOperator
• Decide whether ui_color/ui_fgcolor are needed in SerializedTaskGroup #60466 Decide whether ui_color/ui_fgcolor are needed in SerializedTaskGroup
• Consider create_openapi_http_exception_doc for RTIF endpoint #60467 Consider create_openapi_http_exception_doc for RTIF endpoint

[Vamsi-klu]

Utilized claude code to generate the test and PR details. Open for feedback!

[potiuk]

Can you please split those issues into separate issue per todo and make a description actually readable? We do not neeed those tables and a lot of "noise" generated by claude code. ideally description should describe the gist of a "single" change.

Hopefully the description should be way shorter and easier to read than the code, and it should not describe what was done but why. What is done is visible in the change.

[ashb]

They shouldn't be -- we want to remove these

[Vamsi-klu]

Thanks for the feedback @ashb and @potiuk , i am working on the comments and will raise a revision at earliest

[Vamsi-klu]

Thanks for calling this out. I removed that change from this PR and tracked the removal in #60465 so it can be handled separately.

[Vamsi-klu]

Scoped this PR to a single change (RTIF OpenAPI metadata) and moved the other TODOs into separate issues: #60463, #60464, #60465, #60466, #60467. The branch was force-updated and the PR is now draft for re-review.

[Vamsi-klu]

@potiuk thanks for the feedback. I split the TODOs into separate issues and tightened the PR description to focus on the why; this PR now only documents RTIF OpenAPI metadata (no behavior change).\n\n@ashb the ui_color/ui_fgcolor removal is now tracked in #60465; no change in this PR.