Constant SEARCH_DOC 

pub const SEARCH_DOC: &str = "Search by keyword (default) or semantic similarity. \
     Keyword mode searches posts only; semantic mode searches posts and comments.\n\n\
     `mode=\"keyword\"` (default): Postgres full-text search (`tsvector`/`ts_rank`) over \
     post titles and bodies. Always available. Comments are not searched.\n\n\
     `mode=\"semantic\"`: nearest-neighbor search over post and comment embeddings by \
     cosine similarity, floored so unrelated content isn't padded in just to fill a \
     result count. Finds conceptually related posts and comments that share no \
     keywords. Posts come back in `results`, comments in `comment_results` (each with \
     the title of its post and its similarity); `limit` counts over both \
     together, best match first, and `offset` is ignored (semantic results always \
     start from the best match). Needs the server's embedding backend: a freshly \
     created post isn't embedded yet and won't surface in semantic results for up to \
     ~2 minutes (the embedding sweep interval), and a fresh comment can take longer; \
     content is only ever embedded once, from its original text. If the embedding \
     backend is unavailable, times out, or the server has none configured, the search \
     silently downgrades to keyword instead of erroring \u{2014} check `degraded` and \
     `mode_used` in the response rather than assuming the requested mode ran.";

What search does, in both modes