## Why
The paired thread-environment migration changed several generic test
turn helpers from supplying a fallback cwd to explicitly selecting the
local environment. That changes their meaning under
`build_with_remote_env()`: remote-only fixtures cannot resolve the
forced local selection, so the tests fail before exercising apply-patch,
RMCP, unified-exec, or view-image behavior.
Generic helpers should inherit the environment selected by their
fixture. Tests that intentionally exercise local routing continue to
select the local environment explicitly.
## What changed
- Remove forced `local_selections(...)` overrides from the generic
apply-patch, RMCP, unified-exec, and view-image turn helpers.
- Remove the imports made unused by those deletions.
## Testing
- Not run locally; this is a test-fixture-only change and the `full-ci`
branch will exercise the affected remote shards.