Restructure bin/: deployables at root, tests and tools in subfolders

Only the shipping artifacts (coop_host.exe, coop_hook.dll, coop_hook_x86.dll,
coop_inject_x86.exe, steam_api64.dll, steam_input_actions.vdf) now land in the
bin/<config>/ root, so it can be copied wholesale into a donor game folder. Test
exes (plus the coop_tone fixture) build into bin/<config>/tests/ and the dev probes
into bin/<config>/tools/, via a new coop_output_subdir() CMake helper.

The probes resolve coop_hook.dll / the x86 injector from the deployable root one
level up (new common/coop/tool_paths.hpp: deployed_artifact_path checks next-to-exe
then parent). coop_tone is co-located with the tests so audio_loopback_test's
"spawn coop_tone.exe next to me" lookup is unchanged.

Verified from a clean bin/: root holds only deployables; ctest x64 7/7 and x86 3/3
green (incl. audio_loopback_test driving coop_tone from tests/).

Also convert the roadmap Planned list to bullets and drop this (now-done) item.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/CMakeLists.txt

@@ -107,3 +107,15 @@ target_link_libraries(opengl_hook_test PRIVATE
 	gdi32)
 
 add_test(NAME opengl_hook_test COMMAND opengl_hook_test)
+
+# Keep the bin/<config>/ root deployable: stage every test exe under tests/. coop_tone
+# (the audio_loopback_test fixture) is staged there too, next to its consumer, so the
+# test's "coop_tone.exe alongside me" lookup keeps working.
+coop_output_subdir(tests
+	hook_selftest
+	audio_ring_test
+	audio_loopback_test
+	audio_hook_test
+	srgb_format_test
+	present_hook_test
+	opengl_hook_test)