fix: device nodes incorrectly reported as directories by Dmod_ReadDirEx

[Copilot]

Dmod_ReadDirEx returns Dmod_DirEntryType_Dir for device nodes (e.g. led_ld1 under /dev/dmgpio8/) because dmdrvi_stat_t.mode from the driver can have the DMFSI_ATTR_DIRECTORY bit (0x10) set, and _readdir was assigning it directly to entry->attr.

Changes

• src/dmdevfs.c — _readdir: Clear DMFSI_ATTR_DIRECTORY from entry->attr when populating a device node (file) entry. Device nodes in the file_should_be_listed branch are by definition files; the directory bit must never propagate from the driver's stat mode.

  // Before
  entry->attr = stat.mode;
  
  // After
  entry->attr = stat.mode & ~DMFSI_ATTR_DIRECTORY;

• src/dmdevfs.c — _readdir: Initialize dmdrvi_stat_t stat = {0} to prevent uninitialized memory from leaking into entry attributes when a driver does not populate all stat fields.