Addresses final code review:
- to_int/1 now returns 0 on nil or unparseable strings instead of crashing
- remove unused .pool-row CSS (superseded by .pool-block)
- clamp capacity bar width to [0, 100] to prevent visual overflow
- pool_scrub_line/1 uses scan_function so resilver shows as "resilver..."
Errors produced by Collectors.Host were keyword tuples {:tag, msg}, which
Jason cannot encode — metric push crashed the channel. Convert them to
plain maps with :tag and :message fields.
Reporter.handle_info/2 returned {:ok, socket}, which Slipstream rejects
(GenServer-style {:noreply, socket} is the only valid return for that
callback, unlike handle_connect/handle_join/handle_disconnect).
