feat(coresync): FROST/Influx/Grafana demo + sub-tick burst-window reducer fix

Lands the end-to-end CoreSync demo (frost-influx-grafana.flow.json) along
with the supporting normalizer/identity/interpolation/reducer work, plus
a targeted fix for the under-compression bug surfaced by the FROST demo.

Under-compression fix (PointReducer):
- New burstWindowMs option (default 0, opt-in). When two samples arrive
  within burstWindowMs of each other, the second is treated as the same
  wall-clock observation: previous is replaced, slope analysis is skipped.
- Without this guard, sub-millisecond bursts (rotatingMachine emits twice
  per pressure-injection cycle, ~1 ms apart) produced near-vertical
  apparent slopes that tripped angle-change on every tick — driving
  cog/efficiency/SEC streams to ~0.6% reduction (i.e. no compression).
- With burstWindowMs: 10 in the demo flow, the same streams now compress
  at 78-93% (verified end-to-end in InfluxDB over a 3-min window).
- Editor HTML exposes the new "Burst dt" field with explanatory tooltip.

Regression test (test/basic/coresync.basic.test.js):
- New "burstWindowMs collapses sub-tick sample bursts into a single
  observation" test reproduces the exact burst pattern from the demo
  and asserts before/after behaviour.
- Existing 14 tests continue to pass.

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

coresync.js

@@ -19,6 +19,7 @@ module.exports = function(RED) {
         maxGapMs: Number(config.maxGapMs),
         minDeltaTimeMs: Number(config.minDeltaTimeMs),
         minDeltaValue: Number(config.minDeltaValue),
+        burstWindowMs: Number(config.burstWindowMs) || 0,
         comparisonMode: config.comparisonMode || 'angle',
       },
     });