docs(plan): add 0.5.14 TUI harness optimization

Author: coreyt

dev/plans/0.5.14-todo.md

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+# Airlock 0.5.14 — TODO
+
+## TUI test-harness lifecycle optimization
+
+**Why this is scheduled:** the 0.5.12 release verification ran
+`uv run pytest --tb=short -q -m 'not live' --durations=40`.  The suite reached
+94% quickly, but the final TUI-heavy segment dominated wall time: every entry
+in the slowest 40 was a TUI test, at 14.77–27.62 seconds each.  The full local
+suite took 19 minutes.
+
+Each `AirlockApp.run_test()` constructs all panes and their lifecycle work, not
+just the view asserted by the test.  That includes overview external-probe and
+state-refresh workers, config/MCP refresh, the JSONL tailer, MCP health loop,
+and Textual worker cancellation during teardown.  This is useful integration
+coverage in a few tests, but unnecessarily expensive for simple composition,
+navigation, and rendering assertions.
+
+### Work
+
+- Establish an explicit test-harness mode or fixture that prevents irrelevant
+  background I/O and lifecycle workers while retaining the real widget tree.
+- Migrate pure TUI composition/navigation/rendering tests to that harness.
+- Keep a small, named integration set exercising real worker dispatch,
+  cancellation, shutdown, and the stale-callback guard; do not turn those
+  behaviours into untested mocks.
+- Add duration evidence to the closeout and ensure the full non-live suite
+  remains order-independent.
+
+### Done when
+
+- `pytest --durations=40` shows a material reduction in the TUI-dominated tail.
+- Lifecycle-specific tests still cover `call_from_thread`, worker cancellation,
+  app teardown, JSONL/MCP shutdown, and the OverviewPane stale-refresh path.
+- No production TUI behaviour is gated on the test-harness setting.