fix(serviceMgr): change filter never fires for boolean-valued signals

[UlfBj]

Problem

Subscribing to a boolean-valued signal with a "change" filter never fires a subscription event, e.g.:

{"action":"subscribe","path":"Vehicle.Cabin.Door.Row1.DriverSide.IsOpen","filter":{"variant":"change","parameter":{"logic-op":"gt", "diff":"0"}},"requestId":"233"}

This was tested with logic-op values gt, ne, and lt against a feeder (feederv4) simulating the signal from tripdata.json with alternating true/false values -- the underlying data does change, but no events are ever received, for any logic-op.

Root cause

evaluateChangeFilter (server/vissv2server/serviceMgr/serviceMgr.go) decides whether compareValues should use its "bool" or "number" comparison branch by calling utils.IsBoolean() on the filter's diff parameter, instead of on the signal's own value:

datatype := "number"
if utils.IsBoolean(changeFilter.Diff) {
	datatype = "bool"
}

Per VISS CORE's Change Filter Operation, a boolean signal's diff is conventionally the numeric-looking string "0" -- compareValues' "bool" branch itself requires diff == "0". So utils.IsBoolean("0") is always false for a real boolean-signal subscription, datatype is always forced to "number", and compareValues then tries strconv.ParseFloat("true"/"false", ...), which always fails and silently returns false -- so every change-filter subscription on a boolean path never fires, regardless of logic-op.

This regressed in commit 9714661 ("Subscribe change/range refactoring"), which replaced a previous utils.AnalyzeValueType() call on the signal's own value (which correctly detected bool) with the IsBoolean(diff) check above.

The existing test suite did not catch this: TestCompareValues_Bool* tests call compareValues directly with datatype="bool" hardcoded, bypassing the buggy classification in evaluateChangeFilter entirely; and the one test that did go through evaluateChangeFilter with a boolean signal (TestEvaluateChangeFilter_BoolNe) used an unrealistic diff="false" (which happens to make IsBoolean(diff) true, masking the bug) and asserted nothing about the result (_ = ok // just ensure no panic).

Fix

Classify datatype from the signal's current/latest value instead of from diff:

datatype := "number"
if utils.IsBoolean(currentValue) || utils.IsBoolean(latestValue) {
	datatype = "bool"
}

Testing

• Tightened TestEvaluateChangeFilter_BoolNe to actually assert on the outcome (it previously asserted nothing).
• Added TestEvaluateChangeFilter_BoolWithConformantDiff, a table-driven regression test covering gt/lt/ne/eq with the VISS-conformant diff="0" on true/false transitions -- exactly the bug-report scenario. All 10 subcases pass with the fix (and would have failed before it).
• go test ./server/vissv2server/serviceMgr passes in full.
• go vet ./server/vissv2server/... passes.