fix(pieces,assign): a comma-segment numeral is read by what precedes it (#430, #432)

[derek73]

Closes #430. Closes #432.

They are one boundary, which is why they land together: inside a comma segment a roman numeral is read by what stands before it.

Smith, PSM I     given 'PSM' + suffix 'I'   ->  suffix 'PSM I'
Smith, PSM I.    given 'PSM' + suffix 'I.'  ->  suffix 'PSM I.'
Smith, MD I      title 'MD'  + given 'I'    ->  suffix 'MD I'
Smith, John V.   suffix 'V.'                ->  middle 'V.'
Smith, John V    suffix 'V'                 ->  unchanged, the boundary

Behind a suffix, the numeral describes that suffix — PSM I is Professional Scrum Master level I — so the run continues through it, period included, an initial there being no shape anyone writes. Behind a name, the period is decisive: it marks an abbreviation, which is name material, so the numeral is the middle initial Smith, John B. always was.

Bare after a name it stays the generation (v1 parity, #144). That is why the test is the period, not the numeral.

One cause, two wrong answers

#430's root is rules.md#S2's initial veto in is_suffix_piece — right after a name, wrong inside a credential run — so the segment did not look like a run at all and fell to the given-and-suffix walk. Where the run's first word is TITLES vocabulary too, the leading-title peel took it by a different route instead (Smith, MD I → title MD, given I; Smith, Jr. I via the period-abbreviation inference). A fix verified on PSM alone would have left that half broken and looked green.

Three readers, one reading

The gate that calls a segment a credential run, assign's router that assigns its roles, and group's one-entry join that renders it must agree piece for piece. #429 shipped the inverse of its own fix by deriving that agreement twice, so segment_suffix_reading returns the per-piece verdicts and all three read it (mechanisms.md#ONE-PREDICATE-PER-QUESTION).

The intermediate state proved the point rather than assuming it: with only the gate and the router converted, Smith, PSM I rendered 'PSM, I' — roles right, render split, the same tell as #429 one predicate along.

Declined, and the v1 suite caught it

Asking is_trailing_numeral_suffix for #432's half. It does answer the period question — _ROMAN is anchored and admits no period — but it also refuses a numeral standing behind an initial-shaped piece, which is a no-comma rule and the opposite of this path's parity:

Chang, Andy C I   ->  first 'Andy', middle 'C', suffix 'I'

Asking that predicate here made the numeral a middle and broke that v1 test. decisions.md's #401/#421 entry records the same fork declining to transfer to this walk under LENIENT. Only the period half applies, so only the period half is used.

Verification

Gate	Result
uv run pytest	5702 passed, 221 skipped, 10 xfailed
uv run mypy / ruff	clean
differential 1.4.0 / 2.0.0 / 2.1.0	216 / 176 / 83 intentional, 0 unexplained each

Swept across all three name_orders — identical, these being segment reads rather than positional ones.

Both clauses mutation-checked against a scratch copy: disabling #430's kills three case rows, #432's kills one. Neither guard is inert.

The corpus is not blind to this class

Of 1072 names, three carry a comma then a word then a numeral — Berg, abdul V, Smith, John I, Smith, John V — and all three are bare, the form this change deliberately leaves alone. They are evidence the boundary held rather than an absence of coverage.

Berg, abdul V cannot reach the walk at all: the bound-given join makes abdul V a single piece, which is why the LENIENT mirror #401/#421 declined does not collide here.

The moved names entered the corpora as C1's new examples and carry ledger entries at all three baselines — except #430's at 1.4.0, where fix(comma-family) lone post-comma piece routes to suffix/title, not first already claims the name and a second rule would be dormant.

Not done, recorded rather than left implicit

Neither half emits an ambiguity, though the no-comma John Smith V reports suffix-or-name for the same fork. The comma path has never reported it, #432 raises it as a secondary observation rather than a requirement, and an emitter needs a trigger, a stage-ownership entry and a case row.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.60%. Comparing base (56fb505) to head (ece7721).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #443      +/-   ##
==========================================
+ Coverage   98.59%   98.60%   +0.01%     
==========================================
  Files          45       45              
  Lines        3067     3091      +24     
==========================================
+ Hits         3024     3048      +24     
  Misses         43       43              

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