Add core content definitions

SLICE2.MD

@@ -17,13 +17,13 @@ This slice does not implement gameplay movement, enemy spawning, weapons, or the
 - [x] (2026-04-21 17:04Z) Read repository rules, Windows rules, `PLANS.md`, `DESIGN.md`, `CODE.md`, `SLICE1.MD`, current Godot scripts, and `godot/project.godot`.
 - [x] (2026-04-21 17:04Z) Verified that Slice 1 has committed a bootable Godot shell with `Menu` and `Smoke` debug boot modes.
 - [x] (2026-04-21 17:04Z) Created this Slice 2 ExecPlan.
-- [ ] Implement C# content definition types and validation result types.
-- [ ] Implement sample content registry and intentionally broken validation fixtures.
-- [ ] Add C# test project to the solution and cover registry validation behavior.
-- [ ] Add Godot content browser scene, content browser boot mode, and headless validation-only exit path.
-- [ ] Run formatting for touched C# files with `jb cleanupcode --build=False`.
-- [ ] Validate with .NET tests, .NET build, Godot solution build, and headless content browser boot.
-- [ ] Commit the completed slice.
+- [x] (2026-04-21 17:32Z) Implemented C# content definition types and validation result types.
+- [x] (2026-04-21 17:32Z) Implemented sample content registry and intentionally broken validation fixtures inside tests.
+- [x] (2026-04-21 17:32Z) Added C# test project to the solution and covered registry validation behavior.
+- [x] (2026-04-21 17:32Z) Added Godot content browser scene, content browser boot mode, and headless validation-only exit path.
+- [x] (2026-04-21 17:32Z) Ran formatting for touched C# files with `jb cleanupcode --build=False`.
+- [x] (2026-04-21 17:32Z) Validated with .NET tests, .NET build, Godot solution build, and headless content browser boot.
+- [x] (2026-04-21 17:32Z) Commit the completed slice.
 
 ## Surprises & Discoveries
 
@@ -36,6 +36,12 @@ This slice does not implement gameplay movement, enemy spawning, weapons, or the
 - Observation: There are no existing gameplay content definitions or tests in the repository.
   Evidence: `rg --files` shows only bootstrap, menu, debug smoke scripts and scenes under `godot/`; there is no `tests/` directory.
 
+- Observation: Referencing the Godot C# project from the xUnit project made the Godot source generator run in the test project.
+  Evidence: the first `dotnet test SideScrollerGame.sln` pass printed `CS8785: Generator 'ScriptPathAttributeGenerator' failed ... Property 'GodotProjectDir' is null or empty`. Adding `GodotProjectDir` and `CompilerVisibleProperty Include="GodotProjectDir"` to the test project removed the warning.
+
+- Observation: `.\godot --headless --path godot --build-solutions --quit` generated `.cs.uid` files for every new C# script, including plain content definitions.
+  Evidence: after the Godot build, `rg --files godot\scripts godot\scenes` listed `.uid` files beside all new content and validation C# files. These are kept because Godot generated them for the project scan.
+
 ## Decision Log
 
 - Decision: Implement Slice 2 definitions as plain C# records and small enums inside the existing Godot C# project first, not as Godot `Resource` assets.
@@ -54,9 +60,52 @@ This slice does not implement gameplay movement, enemy spawning, weapons, or the
   Rationale: The jam topic is unknown. Stable ids such as `mission.test`, `enemy.serial`, and `weapon.primary.basic` prove system wiring without committing to a visual or story theme.
   Date/Author: 2026-04-21 / Codex.
 
+- Decision: Keep content definitions inside the Godot C# project for Slice 2 and configure the test project so the Godot source generator has `GodotProjectDir`.
+  Rationale: The Godot project reference worked after the generator property was made visible to the compiler. This preserves the planned `godot/scripts/content/` layout and avoids introducing an extra class library before the content model needs to be shared outside Godot.
+  Date/Author: 2026-04-21 / Codex.
+
 ## Outcomes & Retrospective
 
-Not started. When this slice is completed, update this section with the exact files created, commands run, validation output, and any remaining risks.
+Implemented the core content definition layer under `godot/scripts/content/`, including definitions, registry lookup, validation messages, validation rules, and theme-neutral sample content. Added `tests/SideScrollerGame.Content.Tests/` with xUnit coverage for valid sample content, registry lookup, duplicate ids, missing mission clusters, missing cluster enemies, empty behavior tracks, and invalid difficulty multipliers. Added `ContentBrowser` as a debug boot mode and created `godot/scenes/debug/ContentBrowser.tscn` for in-engine content inspection and headless validation.
+
+Validation completed:
+
+    dotnet test SideScrollerGame.sln
+      Passed!  - Failed: 0, Passed: 8, Skipped: 0, Total: 8
+
+    dotnet build SideScrollerGame.sln
+      Build succeeded.
+          0 Warning(s)
+          0 Error(s)
+
+    .\godot --headless --path godot --build-solutions --quit
+      Exited successfully.
+
+    .\godot --headless --path godot -- --debug-boot=content-browser --content-validate-only
+      Debug boot: ContentBrowser
+      Seed: 1
+      Loaded content definitions:
+      behavior.enemy.parallel
+      behavior.enemy.serial
+      camera.test.path
+      cluster.opening
+      collectible.points.small
+      collectible.squadron.orbit
+      difficulty.easy
+      difficulty.hard
+      difficulty.normal
+      enemy.parallel
+      enemy.serial
+      layer.background.stars
+      layer.foreground.clouds
+      mission.test
+      squadron.orbit
+      weapon.primary.basic
+      weapon.secondary.vertical
+      weapon.special.bomb
+      Content validation succeeded
+
+Remaining risk: the content browser visual layout was validated through headless boot and compilation, not manually inspected in the editor window.
 
 ## Context and Orientation