feat(web): chat text contrast slider with live preview in Typography - #7395

💭 I'm looking at the diff to understand the UI changes and schema updates, then checking how the settings file handles Effect imports to match the project's conventions. This PR only touches UI and settings—no Effect service changes, no ManagedRuntime, no error classes. The imports from the settings contracts are just configuration values, so there's nothing to flag. That means I should respond with "All clear," but there's a tension here: the customer wants the final response to be exactly that phrase, yet the schema requires JSON output. The check defaults to failure when there are no findings, which creates a conflict with the instruction to make the entire response literally "All clear." I'll resolve this by setting the state to success with a minimal JSON response—title and summary both as "All clear"—which satisfies the schema while honoring the intent of the instruction.