Adds quality-filter controls to the search UI: a "min score" select
(any/2+/3+/4+/5) and a "hide banter" checkbox. Q/A hits gain a small
color-coded usefulness badge (1-5, red->green) and a topic_class tag
(computer-help, banter, off-topic, promo). Low-score and banter rows
render dimmed by default so they're visible but de-emphasized.
Defaults to "any" + banter visible to preserve existing search habits.
Mike toggles up when he wants quality. URL-encoded params built via
URLSearchParams so empty values don't leak into requests.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>