Change default strict plan mode setting to enabled (#5714)

* Change default strict plan mode setting to enabled

- Updated default from false to true in state-helpers.ts (primary backend default)
- Updated fallback default in controller/index.ts (Task initialization)
- Updated frontend default in ExtensionStateContext.tsx for consistency
- Fixed linting issue with forEach callback return value
- New users will now have strict plan mode enabled by default
- Prevents file edits in Plan Mode, enforcing cleaner separation of planning vs execution

* added changeset

---------

Co-authored-by: pashpashpash <nik@cline.bot>

docs/docs.json

@@ -214,4 +214,4 @@
 			"copy"
 		]
 	}
-}
+}