Store preferences by model profile

docs/USER_GUIDE.md

@@ -19,9 +19,10 @@ The composer status row shows the current project and, for Git repositories,
 the current local branch. An unsaved draft can be moved with the project menu;
 saved chats keep their original project. Use the branch menu to switch local
 branches when that project's chats are idle. The thinking menu is preselected
-to the model's current mode: **Thinking** is the DS4 default, while **Direct**
-answers without hidden reasoning. **Think Max** is available when the context
-window is at least 393216 tokens, matching DS4's long-context requirement.
+to the active model's default mode and loads that model-and-thinking profile:
+**Thinking** is the DS4 default, while **Direct** answers without hidden
+reasoning. **Think Max** is available when its profile uses at least 393216
+context tokens, matching DS4's long-context requirement.
 
 The **Git** pane shows added, changed, and deleted files from the current
 worktree, including separate staged and worktree markers. Select files to stage,
@@ -66,6 +67,9 @@ Open **View > Model Manager** (`⇧⌘M`) to download, resume, verify, or remove
 supported model artifacts. Preferences choose the active model and control
 generation, context, speculative decoding, Metal execution, SSD expert
 streaming, steering, checkpoint storage, diagnostics, and the local endpoint.
+Generation values are stored per model and thinking mode. Acceleration and SSD
+values are stored per model, while the Prompt section's system prompt is shared
+by every profile.
 
 Model files are large. Verification checks the complete artifact before it is
 used. Removing a model never removes projects or chat history.