docs(command-palette): rewrite guide to match actual implementation

- Updated to reflect 13 tests (6 unit + 7 live_gui) instead of hypothetical async test
- Removed Everything mode and async context preview sections (not yet implemented; marked as future work)
- Updated Commands Registry section to reference actual src/commands.py file
- Added Implementation section with file layout and Command/CommandRegistry/CommandModal reference
- Added Built-in Commands table reflecting the actual 11 commands shipped
- Added Adding Custom Commands section with decorator and explicit-Command patterns
- Added Keyboard Reference table
- Updated Testing section with accurate coverage and test pattern
- Moved unimplemented features (Everything mode, user-defined commands, plugin system) to Future Work

config.toml

@@ -25,7 +25,7 @@ separate_tool_calls_panel = true
 bg_shader_enabled = false
 crt_filter_enabled = false
 separate_task_dag = false
-separate_usage_analytics = true
+separate_usage_analytics = false
 separate_tier1 = false
 separate_tier2 = false
 separate_tier3 = false
@@ -33,7 +33,7 @@ separate_tier4 = false
 separate_external_tools = false
 
 [gui.show_windows]
-"Project Settings" = true
+"Project Settings" = false
 "Files & Media" = true
 "AI Settings" = true
 "MMA Dashboard" = false