feat(collector): capture additional smartctl diagnostics

Record host read and write commands, controller busy time, error log
entries, warning and critical temperature time, and thermal management
transitions from the existing smartctl -a -j acquisition. Schema 7 adds
nullable columns to samples so legacy rows read as unknown, and the
Diagnostics panel shows each counter with its change.

src/fenris/activity_readout.py

@@ -51,8 +51,25 @@ DIAGNOSTIC_COUNTERS = (
     ("unsafe_shutdowns", "Unsafe shutdowns", ""),
     ("media_errors", "Media errors", ""),
     ("available_spare", "Available spare", "%"),
+    ("host_reads", "Host reads", ""),
+    ("host_writes", "Host writes", ""),
+    ("controller_busy_time", "Controller busy time", " min"),
+    ("num_err_log_entries", "Error log entries", ""),
+    ("warning_temp_time", "Warning temperature time", " min"),
+    ("critical_comp_time", "Critical temperature time", " min"),
+    ("thm_temp1_trans_count", "Thermal management 1 transitions", ""),
+    ("thm_temp1_total_time", "Thermal management 1 time", " s"),
+    ("thm_temp2_trans_count", "Thermal management 2 transitions", ""),
+    ("thm_temp2_total_time", "Thermal management 2 time", " s"),
 )
 
+# Reported only by drives that implement thermal management; with no value the
+# panel omits them instead of listing four permanent n/a rows.
+_OPTIONAL_DIAGNOSTICS = frozenset((
+    "thm_temp1_trans_count", "thm_temp1_total_time",
+    "thm_temp2_trans_count", "thm_temp2_total_time",
+))
+
 LOCAL_ACTIVITY_STATE_LABELS = {
     "so_far": "totals so far",
     "incomplete": "incomplete",
@@ -689,7 +706,10 @@ def _counter_deltas(
     inside the window; with fewer than two distinct samples, or across a
     controller-segment change, there is no delta.
     """
-    columns = ", ".join(key for key, _, _ in DIAGNOSTIC_COUNTERS)
+    # A store not yet migrated lacks the newer counter columns: read them as unknown.
+    present = {row[1] for row in conn.execute("PRAGMA table_info(samples)")}
+    columns = ", ".join(
+        key if key in present else "NULL" for key, _, _ in DIAGNOSTIC_COUNTERS)
     columns += ", segment_id"
     last = conn.execute(
         "SELECT id, %s FROM samples WHERE ts <= ? ORDER BY ts DESC, id DESC "
@@ -1016,6 +1036,8 @@ def diagnostics_text(activity: ActivityReadout) -> str:
     for key, label, unit in DIAGNOSTIC_COUNTERS:
         counter = diag["counters"][key]
         if counter["value"] is None:
+            if key in _OPTIONAL_DIAGNOSTICS:
+                continue
             lines.append("%s n/a" % label)
             continue
         delta = "Δ n/a" if counter["delta"] is None else "Δ " + _signed(counter["delta"])