fix(input): free-fly is unreachable, and Escape no longer answers to it

User report: "ESC is hardwired to Freefly which it should not be ... the
freefly should really be discarded. Should not be in the client."

Two separate things were true.

Escape ran a priority chain — cancel target mode, else EXIT FLY MODE, else
leave player mode, else close a window — so in a session that had reached the
free-fly camera, Escape spent itself on that rung instead of doing what the
player expected. The rung is gone; a session somehow in fly mode now falls
through to the next one.

And free-fly was still bound: Ctrl+Shift+F in RetailDefaults (the table
production actually loads) and plain F in AcdreamCurrentDefaults (dead since
K.1c, removed anyway so it cannot be revived by accident). The comment on the
live binding advertised two other ways in — the ImGui View menu and the Debug
panel's "Toggle Free-Fly Mode" button — but BOTH went away with
AcDream.UI.ImGui at Campaign V, so the shortcut was the last route in. It is
now unbound, and a test pins that across both default tables.

This makes free-fly unreachable rather than deleted. The implementation still
spans 25 files (CameraController, FlyCamera, the dispatcher capture, pointer
controller, composition, and a streaming observer source), and ripping that out
at the end of a long session is how a regression lands in the camera. Scoped as
its own follow-up; unbinding is what fixes the reported behaviour today.

The Escape priority test was updated rather than deleted: its middle row now
asserts the fall-through, so the removed rung is documented by a passing test
instead of by its absence.

Solution builds clean; full hermetic gate green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/AcDream.App/Input/GameplayInputCommandController.cs

@@ -239,8 +239,6 @@ internal sealed class GameplayInputCommandController : IGameplayInputCommandTarg
     {
         if (_targetMode.IsAnyTargetModeActive)
             _targetMode.CancelTargetMode();
-        else if (_camera.IsFlyMode)
-            _camera.ExitFlyMode();
         else if (_playerMode.IsPlayerMode)
             _playerMode.ExitPlayerMode();
         else