fix(agent): Make claudeModelsByID available on non-unix platforms

The Windows CI lint-backend step failed with `undefined: claudeModelsByID`
because the helper was defined in claude_test.go, which carries a
`//go:build unix` constraint, while the platform-agnostic
claude_livesettings_test.go calls it. On Windows the unix file is excluded,
so the symbol was missing and the test build failed.

Move claudeModelsByID into the unconstrained claude_mockhelpers_test.go so
it compiles on every platform while staying available to the unix tests.

Author: trustin

backend/internal/worker/agent/claude_mockhelpers_test.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"os"
 	"os/exec"
+
+	leapmuxv1 "github.com/leapmux/leapmux/generated/proto/leapmux/v1"
 )
 
 // spawnMockClaudeAgent spawns os.Args[0] with -test.run=testRun as a mock
@@ -16,3 +18,15 @@ func spawnMockClaudeAgent(ctx context.Context, testRun string, extraEnv []string
 	cmd.Env = append(os.Environ(), extraEnv...)
 	return wireClaudeMockAgent(ctx, cancel, cmd, opts, sink)
 }
+
+// claudeModelsByID indexes converted available models by their ID for
+// order-independent assertions. It lives here, outside the unix-only
+// claude_test.go, so tests that run on every platform (e.g. the live-settings
+// control-response tests) can use it without dragging in unix build tags.
+func claudeModelsByID(models []*leapmuxv1.AvailableModel) map[string]*leapmuxv1.AvailableModel {
+	byID := make(map[string]*leapmuxv1.AvailableModel, len(models))
+	for _, m := range models {
+		byID[m.Id] = m
+	}
+	return byID
+}

backend/internal/worker/agent/claude_test.go

@@ -1983,14 +1983,6 @@ func claudeEffortIDsFromList(efforts []*leapmuxv1.AvailableEffort) []string {
 	return ids
 }
 
-func claudeModelsByID(models []*leapmuxv1.AvailableModel) map[string]*leapmuxv1.AvailableModel {
-	byID := make(map[string]*leapmuxv1.AvailableModel, len(models))
-	for _, m := range models {
-		byID[m.Id] = m
-	}
-	return byID
-}
-
 func TestConvertClaudeModels(t *testing.T) {
 	models := []claudeCodeModelInfo{
 		{Value: "default", DisplayName: "Default (recommended)", Description: "the account default", SupportsEffort: true, SupportedEffortLevels: claudeXHighLevels},