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 Delete the superseded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.

.agents/skills/gig-line-release-qa/references/release-runbook.md

@@ -1,6 +1,6 @@
 # Release Runbook
 
-Authoritative source: `AGENTS.md` (Release Procedure), `docs/RELEASING.md`.
+Authoritative source: `AGENTS.md` (Release Procedure), `docs/process/RELEASING.md`.
 This runbook is the operational checklist; if it conflicts with those, they win.
 
 ## 0. Decide the release
@@ -29,8 +29,8 @@ Files to update:
 | `project.godot` | `config/version="X.Y.Z"` |
 | `CHANGELOG.md` | dated `## [X.Y.Z] — YYYY-MM-DD` entry |
 | `README.md` | latest/current version and summary |
-| `PLAN.md` / `docs/architecture.md` | current version reference |
-| `docs/development-status.md` | shipped capability/release result |
+| `PLAN.md` / `docs/project/architecture.md` | current version reference |
+| `docs/project/development-status.md` | shipped capability/release result |
 | `TODO.md` / `DONE.md` | close/move milestone when complete |
 | `MEMORY.md` | release state and gotchas |