fix: missing Fallback import in AsRaw/AsReal, unused-given warnings in tests

AsRawReal.scala fully-qualified mrpc.Fallback but AsRaw.scala/AsReal.scala
didn't import it at all - never caught locally because the CI test hang
(fixed in #16) meant this branch was never actually compiled end to end
until now.

Also marks the intentionally-shadowed Fallback givens in FallbackSuite/
MetadataFallbackSuite's "normal given wins" tests as @unused - their
presence-but-non-resolution is exactly what's being asserted, which
-Wunused:all -Werror otherwise flags as dead code.

Verified: full `scala-cli test .` passes (0 failed except the pre-existing,
already-documented AnnotationCaptureSuite issue from #16).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: halotukozak

src/mrpc/conv/AsRaw.scala

@@ -1,4 +1,5 @@
-package mrpc.conv
+package mrpc
+package conv
 
 import scala.concurrent.{ExecutionContext, Future}
 import scala.util.Try

src/mrpc/conv/AsReal.scala

@@ -1,5 +1,7 @@
 package mrpc.conv
 
+import mrpc.Fallback
+
 import scala.concurrent.{ExecutionContext, Future}
 import scala.util.Try
 

test/mrpc/conv/FallbackSuite.scala

@@ -2,6 +2,8 @@ package mrpc.conv
 
 import mrpc.Fallback
 
+import scala.annotation.unused
+
 /**
  * DIVERGENCES.md D17: `Fallback[T]` lowers an implicit's priority below normal givens. Proves both
  * halves — a `Fallback`-wrapped instance is picked up when nothing else resolves, AND a normal given
@@ -17,7 +19,8 @@ class FallbackSuite extends munit.FunSuite:
     assertEquals(summon[AsRaw[String, Wrapped]].asRaw(Wrapped("x")), "x")
 
   test("AsRaw: a normal given wins over a Fallback-wrapped competitor, no ambiguity"):
-    given Fallback[AsRaw[String, Wrapped]] = Fallback((_: Wrapped) => "from-fallback")
+    // Present but never actually resolved — that's exactly the point being asserted below.
+    @unused given Fallback[AsRaw[String, Wrapped]] = Fallback((_: Wrapped) => "from-fallback")
     given AsRaw[String, Wrapped] = (w: Wrapped) => "from-normal:" + w.s
     assertEquals(summon[AsRaw[String, Wrapped]].asRaw(Wrapped("x")), "from-normal:x")
 
@@ -26,7 +29,8 @@ class FallbackSuite extends munit.FunSuite:
     assertEquals(summon[AsReal[String, Wrapped]].asReal("x"), Wrapped("x"))
 
   test("AsReal: a normal given wins over a Fallback-wrapped competitor, no ambiguity"):
-    given Fallback[AsReal[String, Wrapped]] = Fallback((_: String) => Wrapped("from-fallback"))
+    // Present but never actually resolved — that's exactly the point being asserted below.
+    @unused given Fallback[AsReal[String, Wrapped]] = Fallback((_: String) => Wrapped("from-fallback"))
     given AsReal[String, Wrapped] = (s: String) => Wrapped("from-normal:" + s)
     assertEquals(summon[AsReal[String, Wrapped]].asReal("x"), Wrapped("from-normal:x"))
 
@@ -37,7 +41,8 @@ class FallbackSuite extends munit.FunSuite:
     assertEquals(instance.asReal("x"), Wrapped("x"))
 
   test("AsRawReal: fromSeparate (built from AsRaw+AsReal givens) wins over a Fallback competitor"):
-    given Fallback[AsRawReal[String, Wrapped]] =
+    // Present but never actually resolved — that's exactly the point being asserted below.
+    @unused given Fallback[AsRawReal[String, Wrapped]] =
       Fallback(AsRawReal.create[String, Wrapped](_ => "from-fallback", _ => Wrapped("from-fallback")))
     given AsRaw[String, Wrapped] = (w: Wrapped) => "from-separate:" + w.s
     given AsReal[String, Wrapped] = (s: String) => Wrapped("from-separate:" + s)

test/mrpc/meta/MetadataFallbackSuite.scala

@@ -3,6 +3,8 @@ package mrpc.meta
 import mrpc.Fallback
 import mrpc.derive.SampleApi.SampleApi
 
+import scala.annotation.unused
+
 /**
  * DIVERGENCES.md D17: `RpcMetadataCompanion.fromFallback` mirrors commons `MetadataCompanion.fromFallback` —
  * a `Fallback[M[Real]]` resolves via implicit search when no normal `given M[Real]` is in scope, but a
@@ -19,6 +21,7 @@ class MetadataFallbackSuite extends munit.FunSuite:
     assertEquals(summon[SimpleMeta[SampleApi]].tag, "from-fallback")
 
   test("a normal given wins over a Fallback-wrapped competitor, no ambiguity"):
-    given Fallback[SimpleMeta[SampleApi]] = Fallback(SimpleMeta("from-fallback"))
+    // Present but never actually resolved — that's exactly the point being asserted below.
+    @unused given Fallback[SimpleMeta[SampleApi]] = Fallback(SimpleMeta("from-fallback"))
     given SimpleMeta[SampleApi] = SimpleMeta("from-normal")
     assertEquals(summon[SimpleMeta[SampleApi]].tag, "from-normal")