test(kmp): make commonTest sources compile on kotlin/native

With the main source sets now compiling on both platforms the native
test compilation finally ran, and it rejected a handful of test-side
forms the jvm toolchain silently accepts.

Backtick test names are mapped onto native symbols, where a comma is
an illegal character, so three names drop the comma; the wording keeps
the same meaning. java.lang.Math.PI has no common analogue and becomes
kotlin.math.PI, matching the already-qualified kotlin.math.sin call on
the same line. String.toByteArray() is jvm-only, and the byte-length
assertion for the APRS line budget switches to encodeToByteArray(),
the same replacement the production sources went through.

core/domain/src/commonTest/kotlin/com/rtbishop/look4sat/core/domain/aprs/AprsBeaconTest.kt

@@ -109,7 +109,7 @@ class AprsBeaconTest {
     @Test
     fun `an over-long comment is trimmed to keep the line legal`() {
         val text = line(comment = "x".repeat(600))
-        assertTrue(text.toByteArray().size + 2 <= 512, "line was ${text.toByteArray().size} bytes")
+        assertTrue(text.encodeToByteArray().size + 2 <= 512, "line was ${text.encodeToByteArray().size} bytes")
     }
 
     /** The comment limit for this format is 43 characters. */

core/domain/src/commonTest/kotlin/com/rtbishop/look4sat/core/domain/aprs/AprsLoginTest.kt

@@ -84,7 +84,7 @@ class AprsLoginTest {
      * every send afterwards reported success against a server that had refused the login.
      */
     @Test
-    fun `an invalid login comment is a refusal, not chatter`() {
+    fun `an invalid login comment is a refusal rather than chatter`() {
         val outcome = AprsLogin.parse(
             "# Invalid login: software name and version are not separated by a space"
         )

core/domain/src/commonTest/kotlin/com/rtbishop/look4sat/core/domain/cw/CwDetectionPoolTest.kt

@@ -156,7 +156,7 @@ class CwDetectionPoolTest {
         var phase = 0
         repeat(4) {
             pool.add(FloatArray(320) { i ->
-                kotlin.math.sin(2.0 * Math.PI * 1500.0 * (phase + i) / sampleRate).toFloat()
+                kotlin.math.sin(2.0 * kotlin.math.PI * 1500.0 * (phase + i) / sampleRate).toFloat()
             })
             phase += 320
         }

core/domain/src/commonTest/kotlin/com/rtbishop/look4sat/core/domain/cw/CwShiftDeciderTest.kt

@@ -132,7 +132,7 @@ class CwShiftDeciderTest {
     }
 
     @Test
-    fun `hysteresis is measured against the anchor, not the previous estimate`() {
+    fun `hysteresis is measured against the anchor rather than the previous estimate`() {
         // Walk in 25 Hz steps: each step is under the 40 Hz margin, so a comparison
         // against the previous estimate would never fire. Anchored, the shift updates
         // once the accumulated move clears the margin.

core/domain/src/commonTest/kotlin/com/rtbishop/look4sat/core/domain/cw/CwToneShifterTest.kt

@@ -121,7 +121,7 @@ class CwToneShifterTest {
      * nothing arrives at — and nothing else in the build would object.
      */
     @Test
-    fun `the shift target sits inside the model window, clear of its edges`() {
+    fun `the shift target sits inside the model window and clear of its edges`() {
         assertTrue(
             CwToneShifter.isInsideWindow(CwToneShifter.TARGET_HZ.toFloat()),
             "TARGET_HZ ${CwToneShifter.TARGET_HZ} is outside the model window " +