fix(k1 tax basis): odd cents of property basis run cumulatively (B-36, D-38)

The tax-basis K-1 shared each entry's built-in gain, property without a
basis, prepaid at book and property distributed among the members entry
by entry, every tied odd cent to the first member: three equal odd-cent
properties contributed 50/50 left the members three cents apart.

Apply D-38's rule (the closes' cumulative largest remainder, through
kernel::apportion_cumulative): tax_capital::RunningSplit keeps each
member's exact running share, rounds the running shares afresh to the
cent and hands out the change, so no member's running share is ever a
cent from exact and tied cents alternate. A negative running whole is
rounded as its magnitude, a zero one by the sign of the whole just
split, so a run of losses mirrors its gains part for part. Exact running
shares are taken to ten places before rounding: a sum of Decimal thirds
can sit a hair under its cent (the law found 399.93 as 399.9299...).

tax_capital::entry_parts runs the splits over every posted entry from
the books' first, in date order, whatever span is asked for, with one
count per set of members with a part in the entry: a member never takes
a cent of an entry they had no part in (Item L's capital contributed is
the basis of the property that member contributed), and the count never
restarts, since its weights are each entry's own amounts, not shares.
An entry's reversal takes its original's split back out of the count
(RunningSplit::unsplit), so an entry's cents are the same in every span
and next year's beginning is this year's ending. The K-1's per-entry
lines come from k1::entry_lines, which k1_detail now uses too.

The book property each member contributed in an entry stays split entry
by entry (each member's property must stay within their own credit);
B-36 says so.

Tests: tied_odd_cents_of_property_basis_run_cumulatively (fails on the
per-entry split: 665.86 / 665.83); a_member_outside_an_entry_never_
takes_its_cents (three members; fails with one count for all members),
an_entrys_odd_cent_is_the_same_in_every_span (a reversal across the
span's start; fails with the count carried span by span or the reversal
not taken out), the_split_runs_in_date_order (fails in posting order);
the law a_running_split_never_drifts_a_cent (5,000 cases: the
largest-remainder rounding of exact integer shares, ties to the first,
and the negated run mirrored; fails with ties to the later member or a
zero running whole rounded as a gain); unit tests for one split,
alternating ties, a member outside a split, the mirror at zero, unsplit
and the thirds case; bookspec example partnership-k1-tax-basis-odd-cents.
rules.md B-36, the handbook (tracing figures), STATUS, testing.md and
verification.md updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

plan/STATUS.md

@@ -189,9 +189,25 @@ its invoices. The handbook's caveat is gone for books with the feature.
   (`wanderbooks books upgrade`, D-39) their invoices and bills still take
   none (the handbook says so).
 - Raised by the cutover review (private change log, "Open points"):
-  ties in the per-entry member split of the tax-basis K-1 all go to the
-  first member (the owner, 2026-10-22: nothing is posted until the
-  year-end close, three weeks off, so it waits).
+  its three points are done. The third (2026-10-22, B-36 with D-38): the
+  tax-basis K-1's odd cents of property basis no longer all go to the
+  first member; they run cumulatively, D-38's largest remainder, one
+  count per set of members with a part in an entry, in date order
+  whatever the span, a reversal taking its original back out
+  (`tax_capital::RunningSplit`, `entry_parts`; tests
+  `tied_odd_cents_of_property_basis_run_cumulatively`,
+  `a_member_outside_an_entry_never_takes_its_cents`,
+  `an_entrys_odd_cent_is_the_same_in_every_span`,
+  `the_split_runs_in_date_order`, the law
+  `a_running_split_never_drifts_a_cent`; bookspec
+  `partnership-k1-tax-basis-odd-cents`). Left as it was, and said in
+  B-36: the book property each member contributed in an entry is still
+  split entry by entry, ties to the first member (each member's property
+  must stay within their own credit in the entry); its odd cents arise
+  only in an entry part cash and part property whose credits don't
+  divide the property evenly. Whether the first company's three-cent
+  gap between its members came wholly from the basis split is to be
+  checked on its books when the K-1 is next run, at the year-end close.
   Its second point is done (2026-10-22, B-14 rule 5): a payment to a
   government (ASC 230-10-45-17(c), "Cash payments to governments for
   taxes, duties, fines, and other fees or penalties") is other operating