Repo hygiene: drop internal planning files, clean docs for publication

Untrack TODO.md, RELEASING.md, RELEASE_NOTES.md, ideas/ and
docs/CLAUDE_PROPER_OBJECT_REGISTRATION_PLAN.md -- internal planning and
agent notes with no reason to be published. Files stay on disk locally.

Replace remaining absolute machine paths in docs with relative ones
(one referenced a separate private project), and swap decorative emoji
for ASCII markers.

README: lead with the no-longer-actively-developed notice.

TODO.md

@@ -1,15 +0,0 @@
-- [x] Setup Atelier #atelier
-
-  Atelier helps you manage AI coding tasks, plans, and TODOs in a visual Kanban board.
-
-  **Getting Started:**
-  - Click **Setup** to configure Atelier with recommended defaults
-  - Or click **Customize** to choose your own settings
-  - Drag items between columns to update their status
-  - Click an item to view and edit its content
-    [Full documentation](https://atelier.dev)
-    [Setup](vscode://Atelier.atelier/customize?agent=claude\&defaults=true) [Customize](vscode://Atelier.atelier/customize?agent=claude)
-- [ ] add scaling to minimapicons
-- [ ] Investigate the functions behind wow.exe lua string.find and find out how to optimize them as they seem to be extremely expensive for the work they do, at least when the game is ran via wine
-- [ ] allow dead player-pets to be selectable in clikthrough
-- [x] adjust our basic settings for atelier to use opus for work as the larger context window is useful