fix(store): no root keeps the \\?\ prefix; the Windows root test compares canonical homes (P11c)

main's canonical default made Root::setup take std::fs::canonicalize(home),
which on Windows is \\?\C:\...  with the long name. root.rs now uses
root::canonical (canonicalize, then the prefix off) at every site, so no
root, record or message keeps the prefix; Unix is unchanged (the identity),
and macOS still agrees on /tmp and /private/tmp. windows_root.rs compares
against default_root(canonical(home)), so TEMP's 8.3 short name is not in
the expectation, and asserts the root has no prefix.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HS8WZziDnyxunC23MUxrLp

crates/ledger-store/tests/windows_root.rs

@@ -35,7 +35,11 @@ fn the_default_root_sits_under_local_app_data() {
 fn setup_makes_a_private_root_and_its_folders() {
     let home = tmp("setup");
     let (root, report) = Root::setup(home.path(), None, None).unwrap();
-    assert_eq!(root.path(), default_root(home.path()));
+    // The default root of the home as the system names it (its long name,
+    // no `\\?\` prefix; TEMP may hold an 8.3 short name).
+    let real_home = ledger_store::root::canonical(home.path()).unwrap();
+    assert_eq!(root.path(), default_root(&real_home));
+    assert!(!root.path().to_string_lossy().starts_with(r"\\?\"));
     assert!(report.created && !report.tightened && !report.recorded);
     assert!(winsec::is_private(root.path()).unwrap());
     for sub in ["books", "run", "legacy"] {