Addresses final code review:
- Host collector's /proc reads now go through Diagnostics.log_read/3,
appearing in commands.log formatted as `$ cat /proc/loadavg`
- configure/1 logs an info line on successful enable so the operator
has a breadcrumb in the journal
- Writer.init/1 documents the deliberate trap_exit omission
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- remove unused .pool-row CSS (superseded by .pool-block)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..."
