Add CUE language support via cue lsp (#1474)

test/resources/repos/cue/test_repo/.gitignore

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+cue.mod/gen/
+cue.mod/pkg/

test/resources/repos/cue/test_repo/cue.mod/module.cue

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+module: "example.com/testrepo"
+language: {
+	version: "v0.16.0"
+}

test/resources/repos/cue/test_repo/lib.cue

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+package testrepo
+
+// #BuildGreeting is a template/closure: given a #Person under `for_`, it produces a #Greeting
+// under `result`. Used by main.cue to build the canonical greeting.
+#BuildGreeting: {
+	for_: #Person
+	result: #Greeting & {
+		recipient: for_
+		message:   "Hello, \(for_.name)!"
+	}
+}
+
+// locales enumerates the locales the greeter supports; defaultLocale (schema.cue) must be one of them.
+locales: [...string] & [
+	"en-US",
+	"en-GB",
+	"de-DE",
+]

test/resources/repos/cue/test_repo/main.cue

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+package testrepo
+
+// alice is a concrete #Person value; used to build the canonical greeting below.
+alice: #Person & {
+	name:  "Alice"
+	age:   30
+	email: "alice@example.com"
+}
+
+// greetingForAlice references both #Greeting (from schema.cue) and #BuildGreeting (from lib.cue).
+greetingForAlice: (#BuildGreeting & {for_: alice}).result
+
+// locale pins the output locale; validated against locales defined in lib.cue.
+locale: defaultLocale

test/resources/repos/cue/test_repo/schema.cue

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+package testrepo
+
+// #Person is the schema for a person record used by main.cue and lib.cue.
+#Person: {
+	name!: string
+	age?:  int & >=0
+	email: string
+}
+
+// #Greeting describes a greeting message addressed to a #Person.
+#Greeting: {
+	recipient: #Person
+	message:   string
+}
+
+// defaultLocale is the fallback locale used when no locale is set on a greeting.
+defaultLocale: "en-US"