Rewrite notes for the single-player architecture

Drop protocol.md; rewrite the tick-loop note around the game-loop-driven sim
and the intent model; rewrite the roadmap (network items removed, sim/game
crate layout, save/load and NPC blocking added); fix crate paths in the
remaining notes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

notes/01-input_manager.md

@@ -2,7 +2,7 @@
 
 ## Current state
 
-Input is fully decoupled from the windowing backend. `client/src/input.rs` owns all input
+Input is fully decoupled from the windowing backend. `game/src/input.rs` owns all input
 types. `main.rs` translates `pbio::Event::Key` events into `GameAction` values each frame and
 stores them in an `InputState`. `game::update()` receives a `&InputState` and queries it with
 three distinct semantics. (The platform/windowing layer lives in the external `pbio` crate;
@@ -10,7 +10,7 @@ game code only ever sees `pbio::Key`, never a raw backend type.)
 
 ## Architecture
 
-### `GameAction` — `client/src/input.rs`
+### `GameAction` — `game/src/input.rs`
 
 Logical actions the game cares about. Game code never sees backend key types.
 
@@ -18,7 +18,7 @@ Logical actions the game cares about. Game code never sees backend key types.
 pub enum GameAction { Up, Down, Left, Right, Confirm, Cancel }
 ```
 
-### `InputMap` — `client/src/input.rs`
+### `InputMap` — `game/src/input.rs`
 
 Translates a `pbio::Key` to an `Option<GameAction>`. All key bindings live here.
 
@@ -31,7 +31,7 @@ Translates a `pbio::Key` to an `Option<GameAction>`. All key bindings live here.
 | Enter            | Confirm |
 | Escape           | Cancel  |
 
-### `InputState` — `client/src/input.rs`
+### `InputState` — `game/src/input.rs`
 
 Three internal buffers, populated from `pbio::Event::Key` events in `main.rs`: