Add blockImages setting to prevent images from being sent to LLM providers

- Setting controls filtering at convertToLlm layer (defense-in-depth)
- Images are always stored in session, filtered dynamically based on current setting
- Toggle mid-session works: LLM sees/doesn't see images already in session
- Fixed SettingsManager.save() to handle inMemory mode for all setters

Closes #492

packages/coding-agent/src/modes/interactive/components/settings-selector.ts

@@ -250,7 +250,7 @@ export class SettingsSelectorComponent extends Container {
 		items.splice(autoResizeIndex + 1, 0, {
 			id: "block-images",
 			label: "Block images",
-			description: "Prevent images from being sent to LLM providers (restart session for full effect)",
+			description: "Prevent images from being sent to LLM providers",
 			currentValue: config.blockImages ? "true" : "false",
 			values: ["true", "false"],
 		});