Reorganize docs into category folders and drop the retired head-review page

Group the top-level docs into docs/project, docs/design, docs/assets and
docs/process, each with its own README index. Delete the superseded
docs/screens/head-review page and sheets. Rewrite every markdown link,
absolute docs path and tool/test reference to the new locations, fix the
pre-existing broken anchors and remove the dead Joke Shop photo-board link.
check_docs OK, Python tooling 167/167.

PLAN.md

@@ -265,7 +265,7 @@ Primary decisions: [ADR-0007](docs/adr/0007-locomotion-and-input-layers.md), [AD
 
 ## Versioning and Delivery
 
-`config/version` in `project.godot` is the single version source (currently `0.9.8`). Releases are tagged `v<version>`; the CI pipeline builds and publishes the standard artifacts plus the optional Desktop HQ zip. Version bumps follow [Semantic Versioning](https://semver.org/): every major, minor and patch increment needs a changelog entry, a local `tools/build_releases.sh` build, and artifact/checksum verification before tagging. Unversioned development tracks do not receive a version until their scope enters a release. See [`docs/RELEASING.md`](docs/RELEASING.md) and [`README.md`](README.md) for commands.
+`config/version` in `project.godot` is the single version source (currently `0.9.9`). Releases are tagged `v<version>`; the CI pipeline builds and publishes the standard artifacts plus the optional Desktop HQ zip. Version bumps follow [Semantic Versioning](https://semver.org/): every major, minor and patch increment needs a changelog entry, a local `tools/build_releases.sh` build, and artifact/checksum verification before tagging. Unversioned development tracks do not receive a version until their scope enters a release. See [`docs/process/RELEASING.md`](docs/process/RELEASING.md) and [`README.md`](README.md) for commands.
 
 ## Gap Analysis