chore: clippy clean across the workspace, all targets

Zero warnings from `cargo clippy --workspace --all-targets`, which is now
a hard rule rather than "clean except pre-existing":

- ChartOfAccounts::add takes the Account it registers instead of eight
  loose parameters (too_many_arguments); Ledger::add_account builds it.
  Same validation, same errors.
- close_period tool: collapse the nested if-let into a let chain.
- iif.rs docs: the IIF layout example shows tabs as `\t` instead of
  literal tab characters (tabs_in_doc_comments).
- Tests: drop an unused binding; assert! instead of assert_eq! against a
  literal bool.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu

crates/ledger-core/src/account.rs

@@ -84,40 +84,20 @@ pub struct ChartOfAccounts {
 impl ChartOfAccounts {
     /// Register an account. Codes must be unique and non-empty; a parent, if
     /// given, must already exist.
-    pub fn add(
-        &mut self,
-        id: AccountId,
-        code: &str,
-        name: &str,
-        account_type: AccountType,
-        parent: Option<AccountId>,
-        placeholder: bool,
-        currency: Currency,
-    ) -> Result<(), LedgerError> {
-        if code.is_empty() {
+    pub fn add(&mut self, account: Account) -> Result<(), LedgerError> {
+        if account.code.is_empty() {
             return Err(LedgerError::EmptyAccountCode);
         }
-        if self.by_code.contains_key(code) {
-            return Err(LedgerError::DuplicateAccountCode(code.to_string()));
+        if self.by_code.contains_key(&account.code) {
+            return Err(LedgerError::DuplicateAccountCode(account.code));
         }
-        if let Some(p) = parent
+        if let Some(p) = account.parent
             && !self.accounts.contains_key(&p)
         {
             return Err(LedgerError::UnknownParentAccount(p));
         }
-        self.by_code.insert(code.to_string(), id);
-        self.accounts.insert(
-            id,
-            Account {
-                id,
-                code: code.to_string(),
-                name: name.to_string(),
-                account_type,
-                parent,
-                placeholder,
-                currency,
-            },
-        );
+        self.by_code.insert(account.code.clone(), account.id);
+        self.accounts.insert(account.id, account);
         Ok(())
     }
 

crates/ledger-core/src/ledger.rs

@@ -7,10 +7,10 @@
 //! audit trail and what will make the future oracle harness trustworthy.
 
 use crate::{
-    AccountId, AccountType, AgingRow, Asset, AssetId, AssetStatus, Bill, BillId, ChartOfAccounts,
-    Class, ClassId, Currency, Customer, CustomerId, DocumentLine, DocumentStatus, EntryId,
-    EntryStatus, Invoice, InvoiceId, JournalEntry, JournalLine, LedgerError, Money, NewAsset,
-    Period, PeriodId, PeriodStatus, Side, Vendor, VendorId, arap, assets,
+    Account, AccountId, AccountType, AgingRow, Asset, AssetId, AssetStatus, Bill, BillId,
+    ChartOfAccounts, Class, ClassId, Currency, Customer, CustomerId, DocumentLine, DocumentStatus,
+    EntryId, EntryStatus, Invoice, InvoiceId, JournalEntry, JournalLine, LedgerError, Money,
+    NewAsset, Period, PeriodId, PeriodStatus, Side, Vendor, VendorId, arap, assets,
     payroll::{
         PayrollAccounts, PayrollLine, PayrollRun, PayrollRunId, payroll_entry_plan,
         payroll_remit_plan, validate_payroll_lines,
@@ -220,15 +220,15 @@ impl Ledger {
     ) -> Result<AccountId, LedgerError> {
         let id = self.next_account_id;
         self.next_account_id += 1;
-        self.chart.add(
+        self.chart.add(Account {
             id,
-            code,
-            name,
+            code: code.to_string(),
+            name: name.to_string(),
             account_type,
             parent,
             placeholder,
-            self.base_currency,
-        )?;
+            currency: self.base_currency,
+        })?;
         Ok(id)
     }
 

crates/ledger-core/tests/invariants.rs

@@ -550,7 +550,7 @@ fn cash_flow_with_registered_asset_and_disposal() {
             false,
         )
         .unwrap();
-    let revenue = ledger
+    ledger
         .add_account("4000", "Service Revenue", AccountType::Revenue, None, false)
         .unwrap();
     let gain = ledger