Collapse the FX-park drain's writes into one undo point instead of one per TrackFX_SetOffline

docs/VERIFICATION.md

@@ -48,6 +48,10 @@ Checks for Θ, Ξ, Ψ, Ε, Ρ, Γ, and Ω work that no unit test can close. Buil
 - [ ] Attempt a mode switch while the transport is playing, then while recording — both refuse, visibly (`docs/COMPLETED.md` §"Ψ-W1-T2")
 - [ ] Click the footer mode segment, save, reopen the project — the mode persisted (`docs/COMPLETED.md` §"Ψ-W1-T2")
 - [ ] `[verify — DAW]` Reproduce the strand: project with FX in both modes, switch to Design, save, close, reopen, toggle to Arrange. Toggle back and forth several more times — the arrangement's FX must NOT converge on permanently offline/hidden. A track the tool refuses to park is NAMED in the console, and the same refusal is not reprinted on a later reapply unless the refused set changed (`src/shell/view/view_fx_park.h`'s `decidePark` / `reportRefusedParks`)
+- [ ] `[verify — DAW]` **The undo collapse.** In a project with several FX across several tracks, switch modes once and count the undo points REAPER shows (Ctrl-Z tooltip / undo history): expect exactly TWO — `ReaSampler: Design View FX park` above `ReaSampler: activate <mode> view` — never one per FX (`src/shell/view/view_fx_park.h`'s `fxParkUndoClose`)
+- [ ] `[verify — DAW]` Then press Ctrl-Z once: every FX re-onlines in that one step and the flags stay parked. A second Ctrl-Z rolls the flags and the ext state back. The FX point must sit ABOVE the switch point, never below it and never folded into it (`src/shell/view/CLAUDE.md` §Invariants — the observed undo semantics)
+- [ ] `[verify — DAW]` Open a project saved in Design mode and check the undo history: the load-tick reapply writes no FX state (they are already offline), so it must add NO undo point at all — the discard form. A `ReaSampler: Design View FX park` entry appearing on a plain project open means the discard is not working (`src/shell/view/view_fx_park.h`'s `fxParkUndoClose`)
+- [ ] `[verify — DAW]` Whether `Undo_EndBlock2` tolerates a `ReaProject*` that closed between it and its `Undo_BeginBlock2`. The drain closes its block unconditionally on the project-gone abort path — an unbalanced block would swallow every later action into one point, which is the worse failure — but the SDK header promises nothing here. Reproduce by closing a project tab while a mode switch's FX drain is in flight (`src/shell/view/view_fx_park.cpp`'s `FxParkUndoBlock`)
 - [ ] `[verify — DAW]` For a track the console names as left unparked, follow the message's recovery IN FULL: re-enable its TCP/mixer visibility, main send and FX enable, **and set every FX in its chain online** (FX enable is the chain bypass — it does not bring an individually offlined FX back). Then switch modes twice: it parks and restores normally, with no further console line. Do the flag half ONLY on a second such track and confirm it is still refused — the FX half of the trust test, and the reason the message spells the step out (unit-tested only as a decision, never against a live chain)
 
 ## Actions and drops