Increase plugin hook env test timeout

[abhinav-oai]

Why

plugin_hook_sources_run_with_plugin_env_and_plugin_source can still fail on Windows after the earlier file-based assertion cleanup because the hook process itself occasionally exceeds the old 5s timeout under CI load. When that happens, the hook run ends as Failed before the test can inspect its structured output.

The Windows Bazel failure showed the hook run itself failing after nearly 8 seconds:

---- engine::tests::plugin_hook_sources_run_with_plugin_env_and_plugin_source stdout ----
thread 'engine::tests::plugin_hook_sources_run_with_plugin_env_and_plugin_source' panicked at hooks/src\engine\mod_tests.rs:428:5:
assertion failed: `(left == right)`
Diff < left / right > :
<Failed
>Completed
...
test result: FAILED. 78 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 7.96s

What

• raise the flaky plugin hook env test timeout from 5s to 10s so it matches the other executed hook tests in this module

Validation

• cargo test -p codex-hooks

[eternal-openai]

approved though I'm concerned that if this took 8s it could still in theory fail at 10s sometimes