feat: add File.stat() method and Stat class for filesystem metadata queries

Implement asynchronous stat() on File class returning a new Stat object with device, inode, mode, linkCount, user, group, specialDevice, size, blockSize, and blockCount fields populated from libuv uv_fs_stat callback. Register foreign method statPath_ in module registry, bump MAX_METHODS_PER_CLASS to 10, add Stat class to io.wren with indexed field accessors, update documentation index with Stat page, and include test coverage for stat on existing file and nonexistent path.

test/io/file/size.wren

@@ -1,13 +1,6 @@
 import "io" for File
 import "scheduler" for Scheduler
 
-System.print(File.size("test/io/file/size.wren")) // expect: 270
-
-// Runs asynchronously.
-Scheduler.add {
-  System.print("async")
-}
-
-System.print(File.size("test/io/file/size.wren"))
-// expect: async
-// expect: 270
+var file = File.open("test/io/file/file.txt")
+System.print(file.size) // expect: 19
+file.close()

test/io/file/size_static.wren

@@ -0,0 +1,13 @@
+import "io" for File
+import "scheduler" for Scheduler
+
+System.print(File.size("test/io/file/file.txt")) // expect: 19
+
+// Runs asynchronously.
+Scheduler.add {
+  System.print("async")
+}
+
+System.print(File.size("test/io/file/file.txt"))
+// expect: async
+// expect: 19

test/io/file/stat_static.wren

@@ -0,0 +1,16 @@
+import "io" for File, Stat
+import "scheduler" for Scheduler
+
+var stat = File.stat("test/io/file/file.txt")
+
+System.print(stat is Stat)            // expect: true
+System.print(stat.device is Num)      // expect: true
+System.print(stat.inode is Num)       // expect: true
+System.print(stat.mode is Num)        // expect: true
+System.print(stat.linkCount)          // expect: 1
+System.print(stat.user is Num)        // expect: true
+System.print(stat.group is Num)       // expect: true
+System.print(stat.specialDevice)      // expect: 0
+System.print(stat.size)               // expect: 19
+System.print(stat.blockSize is Num)   // expect: true
+System.print(stat.blockCount is Num)  // expect: true

test/io/file/stat_static_nonexistent.wren

@@ -0,0 +1,3 @@
+import "io" for File
+
+File.stat("nonexistent") // expect runtime error: no such file or directory