feat: add channel enable/disable, prefab docs, and UI updates

Add per-channel enable/disable toggle to the in-game logging system
with Enable()/Disable() on InGameLogger and EnableChannel/DisableChannel
on IGameLogStore. Update README with prefab setup guide and enable/disable
documentation. Update character creation and log container prefabs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Packages/com.jovian.ingame-logging/README.md

@@ -135,6 +135,32 @@ var tradeLogger = new InGameLogger(logStore, MyLogChannels.Trading);
 tradeLogger.Log("Sold Iron Sword for 50 gold.");
 ```
 
+## Enable / Disable Channels
+
+Each logger can be toggled on or off. When disabled, calls to `Log` are silently dropped (no allocation, no entry added). All channels are enabled by default.
+
+```csharp
+var combatLog = new InGameLogger(logStore, LogChannel.Combat);
+
+combatLog.Disable();
+combatLog.Log("This message is silently dropped.");
+
+combatLog.Enable();
+combatLog.Log("Back online.");
+
+if(combatLog.IsEnabled) {
+    // check state
+}
+```
+
+The state lives in the `IGameLogStore`, so disabling a channel from one `InGameLogger` instance disables it for all instances using the same store and channel. You can also call the store directly:
+
+```csharp
+logStore.DisableChannel(LogChannel.World);
+logStore.EnableChannel(LogChannel.World);
+bool enabled = logStore.IsChannelEnabled(LogChannel.World);
+```
+
 ## Rich Text
 
 Log messages support TextMeshPro rich text tags. The `InGameLogger.Log(message, hexColor)` overload wraps the message in a `<color>` tag automatically:
@@ -194,13 +220,19 @@ logStore.RestoreFromSaveData(saveData);
 - `InGameLogger(IGameLogStore store, LogChannel channel)` -- constructor
 - `void Log(string message)` -- add an entry to the store
 - `void Log(string message, string hexColor)` -- add a color-wrapped entry
+- `void Enable()` -- enable this logger's channel
+- `void Disable()` -- disable this logger's channel (Log calls are silently dropped)
+- `bool IsEnabled` -- whether this logger's channel is currently enabled
 
 ### IGameLogStore / GameLogStore
 
 - `GameLogStore(int capacity = 500)` -- constructor with ring buffer size
 - `int Count` -- current number of entries
 - `int Capacity` -- maximum entries before oldest are overwritten
-- `void Add(LogChannel channel, string message)` -- add an entry
+- `void Add(LogChannel channel, string message)` -- add an entry (silently dropped if channel is disabled)
+- `void EnableChannel(LogChannel channel)` -- enable a channel
+- `void DisableChannel(LogChannel channel)` -- disable a channel
+- `bool IsChannelEnabled(LogChannel channel)` -- check if a channel is enabled
 - `void Clear()` -- remove all entries
 - `void Clear(LogChannel channel)` -- remove entries for a specific channel
 - `ReadOnlySpan<LogEntry> GetEntries()` -- all entries in chronological order