app: remove split implementation

It is completely nonsensical and highly error-prone to have multiple implementations of this in the same build. This should be switched at compile time instead therefore the split packages are pointless.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/strings_linux.go

@@ -0,0 +1,19 @@
+package app
+
+import (
+	"strconv"
+
+	"hakurei.app/internal/app/state"
+)
+
+func newInt(v int) *stringPair[int]            { return &stringPair[int]{v, strconv.Itoa(v)} }
+func newID(id *state.ID) *stringPair[state.ID] { return &stringPair[state.ID]{*id, id.String()} }
+
+// stringPair stores a value and its string representation.
+type stringPair[T comparable] struct {
+	v T
+	s string
+}
+
+func (s *stringPair[T]) unwrap() T      { return s.v }
+func (s *stringPair[T]) String() string { return s.s }