feat: add import keyword token and parser support with updated test syntax

Add TOKEN_IMPORT to the token enum and wire it into the keyword parser in readName(). Refactor string literal parsing by extracting stringConstant() helper that returns the constant index, allowing the new import parser to reuse it. Update all module test files to replace the old .import_() method calls with the new import "module" for Var syntax, and add new error test cases for missing string and missing for clause after import.

test/module/change_imported_value/change_imported_value.wren

@@ -1,5 +1,6 @@
-var Module = "module".import_("Module")
-var Other = "module".import_("Other")
+// TODO: Use comma-separated list.
+import "module" for Module
+import "module" for Other
 
 IO.print(Module) // expect: before
 
@@ -10,5 +11,3 @@ IO.print(Module) // expect: before
 
 // But it does change there.
 Other.show // expect: after
-
-// TODO: Cyclic import.

test/module/cyclic_import/a.wren

@@ -3,7 +3,7 @@ IO.print("start a")
 
 var A = "a value"
 IO.print("a defined ", A)
-var B = "b".import_("B")
+import "b" for B
 IO.print("a imported ", B)
 
 IO.print("end a")

test/module/cyclic_import/b.wren

@@ -3,7 +3,7 @@ IO.print("start b")
 
 var B = "b value"
 IO.print("b defined ", B)
-var A = "a".import_("A")
+import "a" for A
 IO.print("b imported ", A)
 
 IO.print("end b")

test/module/cyclic_import/cyclic_import.wren

@@ -1,4 +1,4 @@
-var A = "a".import_("A")
+import "a" for A
 
 // Shared module should only run once:
 // expect: start a

test/module/implicitly_imports_core/implicitly_imports_core.wren

@@ -1,4 +1,5 @@
-var Module = "module".import_("Module")
+// TODO: Allow omitting "for" clause.
+import "module" for Module
 // expect: Bool
 // expect: Class
 // expect: Fiber

test/module/missing_for.wren

@@ -0,0 +1 @@
+import "module" NoString // expect error

test/module/missing_string_after_import.wren

@@ -0,0 +1 @@
+import for NoString // expect error

test/module/multiple_variables/multiple_variables.wren

@@ -1,8 +1,9 @@
-var Module1 = "module".import_("Module1")
-var Module2 = "module".import_("Module2")
-var Module3 = "module".import_("Module3")
-var Module4 = "module".import_("Module4")
-var Module5 = "module".import_("Module5")
+// TODO: Comma-separated list.
+import "module" for Module1
+import "module" for Module2
+import "module" for Module3
+import "module" for Module4
+import "module" for Module5
 
 // Only execute module body once:
 // expect: ran module

test/module/shared_import/a.wren

@@ -1,5 +1,5 @@
 // nontest
 IO.print("a")
-var Shared = "shared".import_("Shared")
+import "shared" for Shared
 var A = "a " + Shared
 IO.print("a done")

test/module/shared_import/b.wren

@@ -1,5 +1,5 @@
 // nontest
 IO.print("b")
-var Shared = "shared".import_("Shared")
+import "shared" for Shared
 var B = "b " + Shared
 IO.print("b done")

test/module/shared_import/shared_import.wren

@@ -1,5 +1,5 @@
-var A = "a".import_("A")
-var B = "b".import_("B")
+import "a" for A
+import "b" for B
 
 // Shared module should only run once:
 // expect: a

test/module/simple_import/simple_import.wren

@@ -1,4 +1,4 @@
-var Module = "module".import_("Module")
+import "module" for Module
 // expect: ran module
 
 IO.print(Module) // expect: from module

test/module/unknown_module.wren

@@ -0,0 +1 @@
+import "does_not_exist" for DoesNotExist // expect runtime error: Could not find module 'does_not_exist'.

test/module/unknown_module/unknown_module.wren

@@ -1 +0,0 @@
-var DoesNotExist = "does_not_exist".import_("DoesNotExist") // expect runtime error: Could not find module 'does_not_exist'.

test/module/unknown_variable/unknown_variable.wren

@@ -1,3 +1,3 @@
 // Should execute the module:
 // expect: ran module
-var DoesNotExist = "module".import_("DoesNotExist") // expect runtime error: Could not find a variable named 'DoesNotExist' in module 'module'.
+import "module" for DoesNotExist // expect runtime error: Could not find a variable named 'DoesNotExist' in module 'module'.