feat(examples): Basic, a ball simulation with a bug to find

The example was a placeholder that printed which build it was. It is
now a headless simulation of five balls dropped onto a 10 cm floor
slab at 60 ticks a second, with a bug planted the way such bugs are
written: collision is checked only where each step lands, so the ball
dropped from 60 m, at 34 m/s, steps over the slab and falls forever.

It shows the consumer side end to end:
- Basic.DebugShim forwards Pump, Advance, QuitRequested, Log, Check,
  Emit and Sample to Crafter.Debug in debug builds and does nothing in
  plain ones, so the simulation and main have no #ifdef but the
  session's.
- Basic.DebugCommands, compiled only when Debug::Use returns true,
  registers World_Spawn, World_Reset, World_Clear and Ball_Get, and
  watches for the physics, the floor and the balls.
- The simulation checks each ball stays above the floor, emits Bounce
  and samples the fastest ball, so `pause --on-check`, `wait --event`
  and `trace --history` have something to show.

Driven over the real transport, it shows the whole loop: `log --level
warn` names the ball, `pause --on-check` stops the frame it fails,
`set physics.substeps 4` and `call World_Reset` show the fix holds
before any code changes. The plain build simulates ten seconds and
prints that one ball fell through. Its agent notes describe the app
without the bug.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/Basic/interfaces/Basic.DebugShim.cppm

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
+
+// Crafter.Debug's frame-loop and timeline calls, in every build: the real
+// ones under --debug-api, and in a plain build stand-ins that do nothing, so
+// the simulation and main need no #ifdef around them. This is one of the
+// app's own sources, so the define Debug::Use adds reaches it.
+export module Basic.DebugShim;
+import std;
+#ifdef BASIC_DEBUG_API
+export import Crafter.Debug;
+#else
+export namespace Crafter::Debug {
+    inline void Pump() {}
+    inline bool Advance() { return true; }
+    inline bool Paused() { return false; }
+    inline std::uint32_t TakeSteps() { return 0; }
+    inline bool QuitRequested() { return false; }
+    template<class... A> void Log(A&&...) {}
+    template<class... A> void LogWarn(A&&...) {}
+    template<class... A> void LogError(A&&...) {}
+    template<class... A> bool Check(bool ok, A&&...) { return ok; }
+    template<class... A> void Emit(A&&...) {}
+    template<class T> void Sample(std::string_view, const T&) {}
+}
+#endif