feat(store): draft states and discards are journaled, posted_seq is kept (P4)

Accounting reason: a draft that waits on its receipt, and one thrown
away, are facts about the books' working papers that must survive a
restart and replay identically, or a discarded draft would come back and
hold its period open. entry.draft_state_set and entry.draft_discarded are
drafts_v2's (an older version stops at the declaration instead of
misreading them); no figure moves. Schema 19 (taken at merge as the next
after the current last): entries.posted_seq, and a draft_states table
(drafts are not rows of entries, so the plan's entries.draft_state column
has nowhere to live). posted_seq is the journal line that posted each
entry (entry.posted, entry.reversed, the line that closed a period or
posted a schedule month), identical live and on replay.

8.0.6: a hand-written line of each new shape in
books_written_under_older_rules_still_open; fixture old-books/p4_before
written by 25b52580 (hand entries posted late, a reversal, a document, a
schedule month, a recurring draft, open drafts, a close) opens to the
same figures (serialized entries omit a building state, so no golden
moved); drafts_v2_is_its_own_feature; the fuzzer and GUI journal know the
types.

Tests: draft_states_replay_and_project, drafts_v2_waits_for_the_upgrade,
posted_seq_is_the_posting_lines_seq, an_older_version_stops_at_the_draft_events.

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

fuzz/fuzz_targets/fuzz_store_replay.rs

@@ -44,6 +44,7 @@ const TYPES: &[&str] = &[
  "party.w4_set", "party.w9_set", "payroll.taxes_remitted", "reconciliation.completed",
  "reconciliation.voided", "role.assigned", "statement.recorded", "statement.voided",
  "project.set", "entry.settles",
+ "entry.draft_state_set", "entry.draft_discarded",
     // Merged 2026-10-28 (S7, P6): every type EVENT_TYPES names.
 ];
 
@@ -65,7 +66,7 @@ const FIELDS: &[&str] = &[
     "rule", "contributor_adjusted_basis", "fmv_at_contribution", "sec704c_method",
     "tax_basis_723", "depreciable_basis", "built_in_gain_704c", "on", "convention",
     "status", "party_id", "started_on", "ended_on", "links", "notes", "projects",
-    "via", "by", "to", "reference", "note",
+    "via", "by", "to", "reference", "note", "state",
 ];
 
 /// Journal features a `journal.format_set` may declare.