feat(drafts): the drafts tools, the preview digest on every confirm, the digest tool (P4)

Accounting reason: a confirm must act on the thing that was previewed.
Every tool with confirmed (post_entry, reverse_entry, run_schedules,
dispose_asset, reconcile, close_period, create_invoice, create_bill,
write_off_invoice, purge_tin, consolidate_duplicates, and the S6
settlement tools receive_payment and pay_bill, which gain confirmed and
preview on a clone of the ledger) returns preview (SHA-256 of the
canonical preview) and refuses a confirm whose preview is missing or
stale (stale_preview, before anything is written). A draft's digest is
its own state and the settings seq; an operation's is the tool, its
arguments as sent, the settings seq and the journal head seq, so another
session's write forces a re-preview (D-50).

New tools books.list_drafts, books.set_draft_state, books.discard_draft,
books.preview_entry; reports carry as_of_status (drafts open on or before
their end, unreconciled accounts, settings problems) and take strict; the
CPA package is refused while a draft dated in it is open unless
allow_open_drafts gives a reason, journaled as a decision;
books.digest takes since_seq (what was posted since a journal line,
backdated entries included: defect 6) and lists zero_net_accounts,
drafts_by_state and the reconciliation split. Needs attention gains
'draft awaiting receipt' beside 'draft not posted'; the drafts handbook
is rewritten. Every over-the-wire harness confirms the way an agent does.

Docs: mcp-interface, rules B-43, parity, testing (with the For-P12
paragraph), architecture, and the unit's As-built block.

Tests: drafts.rs (a_draft_waits_for_its_receipt_and_posts,
the_gate_moved_and_the_mcp_error_is_unchanged,
a_reversal_needs_no_receipt_of_its_own, discard_unblocks_the_close_over_the_wire,
report_warns_on_draft_before_as_of, cpa_package_refuses_open_draft,
stale_preview_refused, every_confirm_tool_takes_a_preview,
digest_since_seq_is_posting_time, legacy_reversed_replays_identically,
gui_and_server_gate_agree), attention_parity.rs, format_upgrade.rs.

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

crates/ledger-cli/tests/oracle_mcp.rs

@@ -114,7 +114,7 @@ impl Mcp {
     }
 
     fn tool(&mut self, name: &str, args: Value) -> Out {
-        let resp = self.rpc("tools/call", json!({"name": name, "arguments": args}));
+        let resp = common::tools_call(|m, p| self.rpc(m, p), name, args.clone());
         if let Some(e) = resp.get("error") {
             return Out::RpcErr(e.clone());
         }
@@ -1044,6 +1044,15 @@ fn cash_flow_exports_equal_the_core_statement() {
         "books.cash_flow",
         json!({"start": START, "end": END, "cash_accounts": ["1000"], "financing_accounts": ["2100"]}),
     );
+    // (The tool's answer also says what is open as of the end; the
+    // export's file is the statement alone.)
+    let mut tool = tool;
+    assert!(
+        tool.as_object_mut()
+            .unwrap()
+            .remove("as_of_status")
+            .is_some()
+    );
     assert_eq!(tool, j);
 }
 
@@ -3442,7 +3451,8 @@ fn cpa_package_holds_the_year_and_its_evidence() {
     let mut m = Mcp::start(&dir, "1000000.00");
     let out = m.ok(
         "books.export_cpa_package",
-        json!({"as_of": END, "cash_accounts": ["1000"], "include_tins": false}),
+        json!({"as_of": END, "cash_accounts": ["1000"], "include_tins": false,
+                "allow_open_drafts": {"reason": "the test books keep drafts open"}}),
     );
     assert_eq!(out["file"]["file_name"], format!("cpa-package-{END}.zip"));
     assert_eq!(out["file"]["mime_type"], "application/zip");
@@ -3646,7 +3656,8 @@ fn cpa_package_holds_the_year_and_its_evidence() {
     // Without receipts: no evidence at all.
     let out = m.ok(
         "books.export_cpa_package",
-        json!({"as_of": END, "cash_accounts": ["1000"], "include_receipts": false, "include_tins": false}),
+        json!({"as_of": END, "cash_accounts": ["1000"], "include_receipts": false, "include_tins": false,
+                "allow_open_drafts": {"reason": "the test books keep drafts open"}}),
     );
     let files = unzip(&m.handed(&out["file"]));
     assert!(