spotted while bringing syncparty' bufio.[ch] in sync; if the requested len could be bigger than buf->len plus the buf_grow() increment, so we have to iterate. This is currently impossible since we're usign buf_write() only to add one byte.

Add a proper upper limit (4096 seems enough for now) and safely NUL-terminate the rbuf. The idea is to later drop the clt->buf static buffer and allocate it on demand only when we need to do (http) chunking.

Generate the HTML for the filter input in js (it's useless to have it there otherwise) and actually filter the entries. It's a basic case insensitive match, but it's a start. To do so, add dispatch event type X: to mark the end of the playlist so js can replay the filtering.