Documentation that points where the documentation is

The engine documentation, the staged plan, the session handoff and the project
rules are on the wiki now. What is left here is what ships with the engine:
README, LICENSE, install.sh, and this changelog.

The doc comments in ui/panel.rs, ui/routing.rs and editor/assets.rs named
PLAN.md and docs/scripting.md by path; one of them was a markdown link four
directories up, which had stopped resolving the moment the file moved. They
name the wiki page instead. Cargo.toml's platform comment and the .gitignore
note follow.

A changelog, starting now rather than reconstructed. Oxide stays at 0.1.0: the
version is already in Cargo.toml and Phase 1 runs to Stage 16, so the alpha
phase is where it actually is.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

engine/src/ui/panel.rs

@@ -55,7 +55,7 @@
 //! editor canvas previews).
 //!
 //! A future depth-aware mode (where a panel behind a wall is properly
-//! hidden) is in [`PLAN.md`](../../../../PLAN.md)'s Stage-8 backlog and
+//! hidden) is in the wiki Roadmap's Stage-8 backlog and
 //! slots in by attaching a depth attachment to a second pass of the
 //! same pipeline.
 

engine/src/ui/routing.rs

@@ -2,7 +2,7 @@
 //! focus per widget, and tell the host whether the UI captured the frame's
 //! input so the game can decide whether to also handle it.
 //!
-//! Stage 8's UI must *consume input before the game* (PLAN.md): if the
+//! Stage 8's UI must *consume input before the game* (see the wiki Roadmap): if the
 //! cursor is over a button, clicking shouldn't also fire the game-world
 //! action bound to that mouse button. The [`Router`] gives the host one
 //! object to drive each frame: