## Why
Rendering host and executor skill catalogs independently allows their combined
metadata to exceed the skills context budget.
## What changed
- Allocate one budget across both catalogs when both contain model-visible
skills.
- Prefer retaining executor skills when budget pressure requires omissions,
while preserving an executor omission marker and reporting when all host
skills were omitted.
- Evaluate absolute and aliased host paths under the shared budget and select
the rendering that best preserves executor entries, total entries, and
descriptions, in that order.
## Testing
Added renderer and production-turn coverage for shared-budget description
shortening, host-first omission, executor omission markers, and alias selection.
GitOrigin-RevId: 30041736a76aa173cb641aa98a876a306cb437d2