Fix build system: full commit hash, git clean, remove absent USB BINS from base-initfs

- Use full 40-char commit hash in base recipe.toml so the cookbook's
  caching logic correctly recognizes already-fetched sources (short
  hashes always missed the cache, causing patches to re-apply on top
  of already-patched source).
- Add git clean -fd before git reset --hard in fetch.rs so untracked
  files from previous patch applications are removed before re-patching.
- Remove ehcid/ohcid/uhcid from base-initfs BINS list (same fix as
  base recipe, these drivers don't exist in the current upstream).

With these fixes, redbear-live-mini builds and boots to login prompt in QEMU.

src/cook/fetch.rs

@@ -450,6 +450,11 @@ pub fn fetch(recipe: &CookRecipe, check_source: bool, logger: &PtyOut) -> Result
                             recipe_dir.display()
                         );
                     } else {
+                        let mut clean_cmd = Command::new("git");
+                        clean_cmd.arg("-C").arg(&source_dir);
+                        clean_cmd.arg("clean").arg("-fd");
+                        let _ = run_command(clean_cmd, logger);
+
                         // Hard reset
                         let mut command = Command::new("git");
                         command.arg("-C").arg(&source_dir);