Update vendored ANTLR4 grammar to OMG release 2026-05 (daltskin v2026.05.0)

[HansBug]

Summary

This PR refreshes the vendored ANTLR4 grammar from the OMG 2026-03 release to the OMG 2026-05 release (the latest official release, published 2026-07-22). The grammar is generated from the official machine-readable KeBNF by daltskin/sysml-v2-grammar; this PR brings sysmlpy in line with daltskin v2026.05.0 while preserving all of sysmlpy's existing local grammar patches.

Changes and official basis

Change	What changed	Official basis
annotatingMember	: annotatingElement → : memberPrefix annotatingElement	SYSML21-319 "AnnotatingMember does not allow visibility" (SysML 2.1 RTF Ballot 1), implemented in Pilot PR ST6RI-945 #775
payloadFeature	identification now required in the typed alternatives; ownedFeatureTyping / ownedMultiplicity pair normalized; identification-optional specialization alternative added	OMG 2026-05 BNF sync, via daltskin PR #9 "Update grammar to OMG release 2026-05"
framedConcernUsage (2nd alternative)	calculationBody → requirementBody; calculationUsageDeclaration → constraintUsageDeclaration	SYSML21-366 "Error in FramedConcernUsage production" (SysML 2.1 RTF Ballot 1), implemented in Pilot PR ST6RI-945 #775
filterPackage	removed the filterPackageImport ( filterPackageMember )+ alternative and the filterPackageImport : IDENTIFIER /* TODO */ stub (the official 2026-05 KeBNF defines a real FilterPackageImport production; the parser now only uses filterPackageImportDeclaration)	OMG 2026-05 KeBNF update (bnf/SysML-textual-bnf.kebnf)
Regenerated parser sources	SysMLv2Parser.py / SysMLv2ParserVisitor.py / SysMLv2ParserListener.py / .interp / .tokens regenerated with ANTLR 4.13.2 (same version as the currently checked-in generated files); the lexer generated files are untouched (the lexer grammar did not change)	—
grammar/antlr4/README.md	Release tag 2026-03 → 2026-05	—
antlr_parser.py docstring	"generated from the OMG SysML v2 specification (2026-03 release)" → "(2026-05 release)"	—

Each grammar edit carries an inline comment citing the corresponding OMG issue / Pilot PR / BNF production, so the change trail is visible in the .g4 itself.

Downstream impact analysis (why no visitor/classes changes are included)

The four changed productions were checked one by one against the downstream layers (antlr_visitor.py → grammar/classes.py → usage.py/definition.py):

Production	Downstream impact
annotatingMember	The visitor already drops annotating members inside enumeration bodies today (verified: enum def Color { doc /* … */ enum red; } round-trips without the doc member both before and after this change — a pre-existing gap). With this PR, public doc … additionally parses (as required by SYSML21-319), and is dropped the same way. Full round-trip support for enum annotating members (including the visibility prefix) is a separate pre-existing gap, tracked as a follow-up.
payloadFeature	_visit_payload_feature only reads ownedFeatureTyping and falls back to getText(); robust to the alternative reordering. No change needed (verified against the 54-model state-machine corpus: identical results before/after).
framedConcernUsage	The visitor explicitly skips framedConcernMember ("skip for now" in antlr_visitor.py); no change needed.
filterPackage	The visitor already reads filterPackageImportDeclaration() only; the removed stub had no visitor counterpart. No change needed.

What was preserved (and why it must stay)

sysmlpy's local grammar patches are carried over unchanged:

• guardExpressionMember : (IF | GUARD) ownedExpression (guard keyword)
• identification accepts qualifiedIdentification (qualified subject names)
• metadataAccessExpression, invocationExpression, ownedExpression DOT bodyExpression
• view-rendering keywords (COLOR, SHAPE, SHOW, EVENTS, ANNOTATION)
• importRule keeps visibilityIndicator required

These are load-bearing: swapping in daltskin v2026.05.0 verbatim breaks two official fixtures (expression/PathExpressions.sysml, simpletests/EnumerationTest.sysml) in the conformance suite, so a plain "use the exact upstream file" update is not viable.

Note on importRule: daltskin's translation makes import visibility optional, but the official KerML/SysML 2026-05 BNF requires it (Import = visibility = VisibilityIndicator 'import' …, KerML §8.2.3.4.2). sysmlpy's local "required" shape matches the official syntax (a bare import is a syntax error, exactly as the official XPECT fixture Import_Visibility_Valid expects). This local deviation from daltskin is therefore kept, and a comment in the .g4 cites the official production. Related known gap (upstream, not touched here): tests/sysmlv2/validation/valid/Import_Visibility_Valid.sysml has no .error sidecar, so the conformance runner expects a clean parse even though the official fixture expects a syntax error at the bare import — a runner/fixture configuration issue worth a separate fix.

Verification

• The updated grammar was compared rule-by-rule against daltskin v2026.05.0: every changed rule matches upstream exactly (modulo whitespace style and the preserved local patches listed above).
• poetry run pytest tests/grammar_test.py: 95 passed.
• poetry run pytest -m conformance: 111 passed; the 12 pre-existing failures are byte-identical before and after this change (Metadata/Import_Visibility fixtures).
• poetry run pytest tests/ -m "not conformance": 588 passed; the 8 failures are pre-existing (2 PlantUML rendering assertions and 6 missing optional dependencies: networkx/kuzu/cayley), identical before and after this change.
• Quick smoke: state-machine models with transition first … accept … if … then … still parse correctly.

Scope notes

• The conformance fixture corpus under tests/sysmlv2/ is still the 2026-03 XPect suite (unchanged). Updating it to the 2026-05 suite can be a follow-up PR.
• AnnotatingMember now accepts an explicit visibility in the parser; full object-model round-trip of enum annotating members (with or without visibility) remains a pre-existing gap and is a candidate follow-up.

Happy to adjust anything.