ekp/.phrase/phases/phase-kp-overhaul-20260726/plan_test_isolation_20260728.md

Plan: ERT State and Order Isolation

Scope

Resolve issue004: make the parshape dispatch regression truthful, restore all test-owned EKP configuration, and make order dependence observable.

Resolution Path

1. Reproduce the named parshape test alone with the C module loaded.
2. Drive the public formatter with a real parshape and an observable C-call negative control.
3. Dynamically bind every mutable EKP option and spacing state owned by the shared clean-state fixture.
4. Add public-ERT-API runners for reproducible permutation and one fresh Emacs process per test.
5. Run the focused matrix, full permutation, full isolation, compilation, and checkdoc.

Non-goals

• No test framework dependency.
• No reliance on private ERT functions.
• No production formatter change.

Rollback

Restore the partial fixture and default runner, then remove the new permutation/isolation entry points and CI step. No persisted data changes.