feat: live monitor TUI (M2) — 0.21.0

Upgrade `rigdoctor monitor` from a basic redraw to a stdlib curses dashboard
(tui.py): current / session-min / session-max per sensor, grouped by subsystem,
with temperature & utilization color bands (GPU-lost flagged red). q quits,
r resets min/max. Plain full-screen redraw fallback on a non-TTY (--plain forces
it). Pure track()/band() helpers are unit-tested; curses path verified in a pty.

Completes the Monitoring bundle (M2 + M8).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_tui.py

@@ -0,0 +1,58 @@
+"""Tests for the M2 live-monitor TUI logic (min/max tracking + color bands)."""
+
+import unittest
+
+from rigdoctor import tui
+from rigdoctor.core.sample import Reading, Sample
+
+
+def _temp(v):
+    return Reading("gpu", "temp", v, "°C", "")
+
+
+class TrackTests(unittest.TestCase):
+    def test_tracks_min_and_max(self):
+        stats: dict = {}
+        for v in (60.0, 80.0, 70.0, 55.0):
+            tui.track(stats, Sample(0.0, [_temp(v)]))
+        self.assertEqual(stats["gpu.temp"], (55.0, 80.0))
+
+    def test_ignores_none_values(self):
+        stats: dict = {}
+        tui.track(stats, Sample(0.0, [_temp(None)]))
+        self.assertEqual(stats, {})
+
+    def test_keys_separate_by_label(self):
+        stats: dict = {}
+        tui.track(stats, Sample(0.0, [
+            Reading("cpu", "temp", 50.0, "°C", "Core 0"),
+            Reading("cpu", "temp", 70.0, "°C", "Core 1"),
+        ]))
+        self.assertEqual(stats["cpu.temp.Core 0"], (50.0, 50.0))
+        self.assertEqual(stats["cpu.temp.Core 1"], (70.0, 70.0))
+
+
+class BandTests(unittest.TestCase):
+    def test_temperature_bands(self):
+        self.assertEqual(tui.band(_temp(40.0)), "cold")
+        self.assertEqual(tui.band(_temp(60.0)), "good")
+        self.assertEqual(tui.band(_temp(80.0)), "warn")
+        self.assertEqual(tui.band(_temp(90.0)), "crit")
+
+    def test_usage_bands(self):
+        self.assertEqual(tui.band(Reading("gpu", "util", 50.0, "%")), "good")
+        self.assertEqual(tui.band(Reading("gpu", "util", 88.0, "%")), "warn")
+        self.assertEqual(tui.band(Reading("memory", "used_pct", 96.0, "%")), "crit")
+
+    def test_non_metric_percentage_is_normal(self):
+        self.assertEqual(tui.band(Reading("gpu", "fan", 100.0, "%")), "normal")
+
+    def test_gpu_lost_is_crit(self):
+        self.assertEqual(tui.band(Reading("gpu", "status", None, "", "query-timeout")), "crit")
+
+    def test_missing_value_is_na(self):
+        self.assertEqual(tui.band(Reading("gpu", "power", None, "W")), "na")
+
+
+if __name__ == "__main__":
+    unittest.main()