Add project skeleton: Godot setup, tooling, and smoke test

Pins Godot 4.6.3-stable and GUT 9.6.0 (9.6.1+ reference
AccessibilityServer, unavailable in 4.6.3) via tools/setup.sh. Wires
make check (gdlint + gdformat config for 4-space indent, headless
GUT run, and a JSON well-formedness check ahead of real schema
validation). Seven autoload stubs match the architecture in the
cahier des charges; real logic lands with the following steps.

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

tests/test_bootstrap.gd

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+extends GutTest
+## Verifie que le squelette du projet charge correctement les sept autoloads.
+## Les tests de logique pedagogique (correction, progression, sauvegardes)
+## arrivent avec les etapes correspondantes.
+
+
+func test_autoloads_are_registered() -> void:
+    assert_not_null(GameManager, "GameManager doit etre charge")
+    assert_not_null(ProfileManager, "ProfileManager doit etre charge")
+    assert_not_null(ProgressManager, "ProgressManager doit etre charge")
+    assert_not_null(ExerciseEngine, "ExerciseEngine doit etre charge")
+    assert_not_null(SaveManager, "SaveManager doit etre charge")
+    assert_not_null(AudioManager, "AudioManager doit etre charge")
+    assert_not_null(SettingsManager, "SettingsManager doit etre charge")

tests/test_bootstrap.gd.uid

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+uid://bgko12vcwsipr