Fix pinned todos config-off test isolation

[1jehuang]

Summary

• explicitly force JCODE_PIN_TODOS=0 in the config-off test
• invalidate the configuration cache before creating the test app
• reuse the existing guard cleanup so later tests cannot inherit stale state

Verification

• cargo test -p jcode-tui --lib tui::app::tests::pinned_todos_payload_stays_empty_when_config_off -- --exact --test-threads=1

Fixes #877

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— Jcode agent (automated triage), on behalf of @1jehuang

[1jehuang]

CI follow-up: the formatting gate now passes. The remaining Quality Guardrails failure is the repository-wide code-size baseline, which reports the same pre-existing growth across unrelated files on all three branches; this PR does not update that baseline. Platform build/test jobs are still queued.

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— Jcode agent (automated triage), on behalf of @1jehuang

[greptile-apps]

Greptile Summary

This change makes the pinned-todos config-off test explicitly disable the inherited JCODE_PIN_TODOS setting and invalidate cached configuration before creating the application. The exact test failed on the parent revision when JCODE_PIN_TODOS=1 was inherited, then passed at the PR head under the same condition, confirming that the configuration-off behavior is now isolated. The desktop source changes are formatting-only.

Confidence Score: 5/5

Safe to merge; the targeted test now behaves correctly even when the process inherits an enabled pinned-todos environment setting.

The changed failure path was exercised directly on both revisions: the parent revision failed with the inherited override, while the PR revision passed under the identical override. No remaining defects were found.

Files Needing Attention: No files need further attention.

T-Rex Logs

What T-Rex did

• Ran the pre-fix pinned-todos test with the inherited environment override and observed a failure.
• Reran the pinned-todos test at PR head; the test passed.
• Compared the before-and-after runs to confirm that disabling the environment override and invalidating cached configuration isolates the config-off test.
• Captured the before-command log showing a failure after 0.25s for the pinned-todos test in the temporary workspace.
• Captured the after-command log showing a successful run on HEAD after 0.04s, with no publishable regression.

_{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "style: apply workspace formatting" | Re-trigger Greptile}