feat(package): one attention engine over PackageBooks (U0b)

Needs attention was computed by the viewer alone, while books.start
hand-picked a handful of next steps. The human's list and the agent's
could disagree, and a new item had to be written twice (or, as
books.start showed, not at all).

Move the engine to ledger-package over PackageBooks: one function,
find/find_with(books, today, settings, integrity), reads the ledger, the
journal's event types (an entry's origin), the attachments and their
links, the statements, the reconciliations, and the database check. The
viewer's attention module now only maps Target to Route; books.start
turns the same items into its next steps (why = the item's title, top 12),
so the list the human sees and the steps the agent gets cannot drift.

PackageBooks gains settings, journal, statements, reconciliations and
disk_check, implemented for Store and Snapshot, so both views answer
alike. The W-9, reconciliation and 1099 predicates move beside the items
to keep one copy. ledger-package gains ledger-config and serde_json (the
receipt policy and the tool arguments the items carry).

Tests: view_model.rs and spec_kept.rs pass unchanged; the new
attention_parity.rs compares the viewer and books.start item for item on
the demo books and on a book written entry by entry. just check green.

docs/testing.md

@@ -2915,3 +2915,50 @@ example" arm; the adapter's `event_of`, its `depreciation_schedule` month
 span (acquisition through as-of, 0.00 where the schedule reaches no month)
 and every `answer_*` figure against the loader's same check (the two must
 agree on all 56 examples).
+
+## U0b: one attention engine over `PackageBooks` (2026-10-26)
+
+Needs attention moved out of the viewer into `ledger-package::attention`
+(D-53): one function, `find`/`find_with(books, today, settings, integrity)`,
+over the `PackageBooks` trait (`Store` and `Snapshot`). The viewer's
+`ledger-gui::attention::find` is now a mapping (`Target` → `Route`,
+`Severity` → the viewer's); `books.start` turns the same items into next
+steps, `why` equal to the title, at most 12. `PackageBooks` gained
+`settings`, `journal`, `statements`, `reconciliations` and `disk_check`, so
+the engine can read an entry's origin from the journal's event types (as
+the viewer's builder did) and the same statements, reconciliations and
+database check through either view.
+
+- **ledger-package (unit tests in `src/attention.rs`):** none of its own
+  (the engine's conditions are exercised end to end); the crate's tests
+  (`cargo test -p ledger-package`) keep the package over `Store` and
+  `Snapshot` equal.
+- **ledger-gui:** `tests/view_model.rs` passes unchanged (the viewer's
+  list is the engine's); `src/attention.rs`'s unit tests
+  (`cash_flow_warnings_are_items`,
+  `a_stale_rule_asks_for_the_authority_and_the_humans_confirmation`) move
+  with it and pass; `tests/assets.rs`, `tests/attachments.rs`,
+  `tests/edges.rs`, `tests/old_books.rs`, `tests/parties.rs`,
+  `tests/spec_gui.rs` exercise the items through the viewer's wrapper.
+- **ledger-cli:** `tests/attention_parity.rs`
+  `the_viewer_and_books_start_see_the_same_attention` (the demo books and a
+  book written entry by entry: the viewer's titles, in order, are exactly
+  `books.start`'s attention steps).
+- **unchanged:** `crates/ledger-cli/tests/spec_kept.rs`'s `books.start`
+  tests (the fixed steps keep their order; attention items sit between the
+  backup step and the focus).
+
+**For P12 (mutation targets, none run, D-33):**
+`ledger-package attention`: `origin`'s arm order (a reversal before its
+schedule, a bill before its payment) and `entry_refs`' keys;
+`missing_receipt`'s conjunction (the `Journal entry | Recurring` origin,
+`reversal_of` none, no receipts, the policy); the `> 3` combine and its
+`try_fold`; `w9_missing`'s three clauses (no W-9, files a 1099, the vendor
+not marked on file) and `files_1099`'s `any`; `paid_this_year`'s `max`
+(today) and `min` (Dec 31) and its `paid - received`; `depreciation_due`'s
+`in_effect` filter, its `period_month` (`1..=12`) and its `!is_zero`;
+`period_month`'s split; the severity arms (undetermined 1099, refuse
+tax category, parties require); `dollars`' thousands grouping and its
+negative-zero test; `filter(|a| a.tool.is_some()).take(12)` and
+`step_title`'s 160-character cut in `start_out`; the viewer wrapper's
+`Target` arms.