P3: rename accounts, one set of period defaults, tax categories warn or refuse (defects 15, 16, 8)

books.rename_account; account names trimmed, bounded, refused when a
sibling's or TIN-shaped; books.show refuses what its target ignores. A
report asked for without dates covers this fiscal year so far, everywhere
(one rule for tools, descriptions and the viewer; the IIF and CPA package
keep their own dates). policy.require_tax_category warns or refuses; a
Form 4797 gain is shown apart on every return.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-gui/tests/spec_gui.rs

@@ -1064,8 +1064,18 @@ fn small_books(tag: &str) -> Small {
     let cash = store
         .add_account("1000", "Checking", AccountType::Asset, None, false)
         .unwrap();
+    // Mapped to the return, so books with nothing else to do have
+    // nothing in Needs attention (rules.md B-32 lists every expense
+    // account without a category, used or not).
     let rent = store
-        .add_account("6100", "Rent", AccountType::Expense, None, false)
+        .add_account_with_tax(
+            "6100",
+            "Rent",
+            AccountType::Expense,
+            None,
+            false,
+            Some(("rent_property", None)),
+        )
         .unwrap();
     Small {
         dir,