docs(plan): Q-9 answered (D-61): the reader crate, unit U0d after S4.5

The owner, 2026-10-29, the question tool: the reader (`extract.rs`)
moves into a small library crate of its own, `ledger-reader`, that
`ledger-store` and `ledger-import` both depend on, so the writer sheds
the typesetter and the crate map is layered again; half a day for the
implementing team once S4.5 is in. 8.2 gains the unit U0d in the
template (its Done-when is `cargo tree`), 8.0.1 its row, 8.0.3 the
crate name (D-53's closed `ledger-extract` subprocess stays closed),
10.1 D-61, 10.3 closes Q-9. STATUS.md, HANDOFF.md and architecture.md
say the same; the arrow stands as built until U0d lands.

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

plan/HANDOFF.md

@@ -18,14 +18,14 @@ You are the engineering manager (EM) of a team implementing the remaining work o
 
 - `main` is `bfd453b6`. Landed since the hand-off: U0a, U0b, U0c, P7, P9a, P13 steps 1-3, P4b S4.1, S4.2, S4.3 (2026-10-26 to 2026-10-27), then S4.4, S5, S6, S7 and P6 (2026-10-29, merged from the paused branches by the planning session). Live on the owner's books: P0 to P3, Projects, P4b S1 (`document_standing`); everything behind `documents_v2` waits for the owner's upgrade (Q-5).
 - Nothing is built and unmerged. Branch `ci-fixes` (`76285434`, a fuzz target's renamed path and a regression test) is the one branch left to merge.
-- Not started: S4.5 (next), P4, P5, P8, P10, P11a (starts now: D-56; step 0 first), P11b, P12, P13 steps 4-6.
+- Not started: S4.5 (next), U0d (after S4.5), P4, P5, P8, P10, P11a (starts now: D-56; step 0 first), P11b, P12, P13 steps 4-6.
 - The plan's section 8 was rewritten on 2026-10-26 for this hand-off and revised on 2026-10-28 (section 0, "What changed on 2026-10-28"; `plan/2026-10-28_DRIFT_REPORT.md`). Sections 1 to 7 are the older design and carry strike-throughs (`~~text~~ → D-n`) and "As built" notes where the build or a decision departed; where section 8 and an earlier section disagree, section 8 is right.
 - Mutation testing is paused until unit P12 (decision D-33). Workers never run `cargo mutants`; each unit writes a "For P12" paragraph in `docs/testing.md` instead (recipe R-G).
 - The owner's live books are never touched by anyone on this team. The only books a worker uses are test fixtures and throwaway books made by `wanderbooks setup` in a scratch root. A unit's new writes are refused on the owner's books until the owner's format upgrade; merging never waits for that.
 
 ### The paused worktrees (2026-10-27 pause) landed on 2026-10-29
 
-Nothing is left to resume. The merges went in the 8.0.2 order with the conflicts that paragraph predicted; what P6's first complete gate found is in its As-built block (8.2) and `plan/STATUS.md`. Two lessons for the next pause: a checkpoint whose gate was interrupted is not a reviewed unit (P6's five unreached tests and the write-off interaction cost a day of gates), and in this colocated repo never run a `jj` command while a `git merge` is in progress in the same checkout (jj's auto-import resets git's index; one merge had to be redone in a scratch worktree). Q-5 and Q-8 were answered 2026-10-28 (D-57, D-58); Q-9 (P6's `ledger-store` → `ledger-import` dependency) is with the owner.
+Nothing is left to resume. The merges went in the 8.0.2 order with the conflicts that paragraph predicted; what P6's first complete gate found is in its As-built block (8.2) and `plan/STATUS.md`. Two lessons for the next pause: a checkpoint whose gate was interrupted is not a reviewed unit (P6's five unreached tests and the write-off interaction cost a day of gates), and in this colocated repo never run a `jj` command while a `git merge` is in progress in the same checkout (jj's auto-import resets git's index; one merge had to be redone in a scratch worktree). Q-5 and Q-8 were answered 2026-10-28 (D-57, D-58); Q-9 on 2026-10-29 (D-61: the reader moves into its own crate, unit U0d, after S4.5).
 
 ### How to run things