polish: complete the RGL enough to build an application grammar

Adding Polish to informath (grammars/next) exposed a set of gaps. Unlike
Czech, StructuralPol was already complete; what was missing was a handful
of lins, a way to govern the nominative, and some outright mistakes.

Missing lins, all reached as qualified Grammar.X by the application's
functors and so not shimmable from the application side:

  AdjectivePol  AdvAP
  SentencePol   SSubjS
  IdiomPol      ImpP3
  StructuralPol that_Subj
  MarkupPol     new module (Markup is not part of the RGL build script,
                so it is compiled on demand, as MarkupCze is)
  ParadigmsPol  mkAdv (every other ParadigmsX has it; the application
                interfaces reach it as Paradigms.mkAdv)

ImpP3 has no third-person imperative to use, so it takes the standard
"niech" periphrasis. The copula takes the future ("niech x będzie grupą")
and every other verb the present ("niech x należy do A"): być is the only
Polish verb with a synthetic future, and imienne marks exactly the copular
VPs.

NomPrep: ComplCase had no nominative at all, so "jako", "niż" and
"zdefiniowany jako" -- all of which govern the nominative -- came out
locative ("mniejszy niż liczbie"). mkCompl now maps Nom to a new NomPrep,
and the dep tables of the pronouns, nounPN, mkPN and the structural NPs
cover it. LexiconNounPol is marked DO NOT EDIT, but paris_PN and john_PN
inline their own dep tables and so had to be extended too.

Two corrections:

  VerbPol.CompCN used the nominative for a predicative noun, giving
  "x jest grupa"; Polish uses the instrumental, as CompNP right below it
  already does.

  ExtendPol.ExistsNP inherited ExistNP from ExtendFunctor, giving
  "jest macierz". Polish distinguishes the two: "there exists" is istnieć,
  which is what mathematical prose uses.

ParadigmsPol.guess_paradigm_basic never matched -ość, the productive
feminine abstract suffix, so sprzeczność took a masculine declension
(*sprzeczności/a, *sprzecznościowi) despite being tagged feminine. It now
routes to the kość paradigm.

Also documents, without changing, why the 2-string mkN throws its genitive
away: guess_paradigm's 2-string table is unsound (its first branch matches
every noun in -a, and its branches disagree about whether mkNTable* takes
the nominative or the bare stem), so passing sggen to it turns
"liczba"/"liczby" into *liczbaa. The 1-string guesser is the sound path
until that table is repaired.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/polish/StructuralPol.gf

@@ -87,6 +87,9 @@ lin
   something_NP  = cos ;
   somewhere_Adv  = ss "gdzieś";
   that_Quant = demPronTen "tamten";
+  -- Polish always sets off a "że" clause with a comma, so the subordinator
+  -- carries it, as IdiomPol/SentencePol already do for EmbedS and SlashVS
+  that_Subj = ss [", że"];
   there_Adv = ss "tam";
   there7to_Adv = ss "tam";
   there7from_Adv = ss "stamtąd";