B2.3 + P11.1 + P11.2 + monster schema fix

B2.3 LatestWinsGate fireAndWait:
  Added fireAndWait(value, ctx?) returning per-fire settlement promise.
  Supersede resolves with frozen sentinel {superseded: true} (no
  rejection — callers branch on value without try/catch). Dispatch
  errors also resolve (with undefined); error surfaces via gate.lastError.
  LatestWinsGate.js 75 → 116 lines. 12/12 tests pass.

P11.1 convert.possibilities(measure):
  New helper returning sorted+deduped unit names for a measure.
  Cached per measure. Reuses existing convert measures map. Also
  exposed convert.measures() listing all known measures.
  convert/index.js +21 lines. New test file: 90 lines, 12/12 tests.

P11.2 commandRegistry.units field:
  Pre-dispatch normalisation pipeline. descriptor.units = {measure,
  default}; commandRegistry extracts msg.payload + msg.unit (3 shapes),
  validates against measure, converts to default, falls back + warns
  with accepted-list on unknown/wrong-measure. Falls back gracefully
  if convert.possibilities is missing. commandRegistry.js 164 → 237.
  +7 new tests covering all 4 paths.

monster schema fix (P11.2 sibling):
  generalFunctions/src/configs/monster.json was stripping four
  legitimate constraint keys (nominalFlowMin, flowMax, maxRainRef,
  minSampleIntervalSec). Added them with defaults matching the
  legacy nodeClass coercion. Side effect: this also UNBLOCKED the
  monster cooldown-guard test (separate ROOT-CAUSE entry below).

CONTRACTS.md §4 + §8 updated. 144/144 basic tests + 206/206 full
generalFunctions tests pass.

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

src/configs/measurement.json

@@ -439,6 +439,16 @@
             "description": "Channel map used in digital mode. Each entry is a self-contained pipeline definition: {key, type, position, unit, scaling?, smoothing?, outlierDetection?, distance?}. Ignored in analog mode."
         }
     },
+    "calibration": {
+        "stabilityThreshold": {
+            "default": 0.01,
+            "rules": {
+                "type": "number",
+                "min": 0,
+                "description": "Absolute standard-deviation ceiling (in scaling-units, i.e. the same range as absMin..absMax) below which the rolling window is considered stable enough to trust for calibration / repeatability. A buffer with stdDev <= threshold is treated as stable; anything above aborts calibrate() and evaluateRepeatability() with a warning. Default 0.01 fits the [50,100] absMin/absMax default range; tighten or relax to match your sensor's expected noise floor."
+            }
+        }
+    },
     "outlierDetection": {
         "enabled": {
             "default": false,