* fix(exec): treat exact empty workdir as omitted
Small tool-calling models fill every optional field of the exec schema,
so exec arrives with workdir: "" instead of omitting the field. The
empty string was treated as a literal path and the command was refused,
wasting agent turns and surfacing misleading failures (e.g. the model
concluding the runtime is unavailable).
Normalize only the exact empty string to omitted at the workdir input
boundary; whitespace-only and nonempty invalid paths remain fail-closed.
Closes#126390
* fix(exec): align exec schema with empty-workdir behavior
The shared model-facing schema still declared blank and whitespace
workdirs invalid while the resolver now treats an exact empty string as
omitted. Update the schema description to state that an empty string
means omitted and only whitespace-only values are invalid, and update
the schema assertion accordingly.
Hüseyin
6132c6f6cb