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/src/pages/cash.rs

@@ -105,7 +105,7 @@ pub fn show(ui: &mut Ui, b: &Books, shell: &mut Shell<'_>) {
                     },
                 );
                 if r.interact(Sense::click()).clicked() {
-                    shell.state.accounts.range = None;
+                    shell.state.accounts.range = crate::pages::accounts::RegisterRange::Default;
                     shell.go(Route::Account(*id));
                 }
             });