Error-set convergence now lives in src/ir/error_analysis.zig behind a *Lowering
facade (ErrorAnalysis), mirroring the other domain extractions. Moved verbatim:
- convergeInferredErrorSets (whole-program inferred-`!` SCC fix-point),
- convergeClosureShapeSets,
- collectErrorSites / collectClosureShapes (the AST collectors).
Added ErrorFacts (the PLAN-ARCH shape: inferred_error_sets + shape_inferred_sets)
+ a facts() view over the maps, which stay on Lowering for now (consumers read
them via self.*). recordClosureShape and its deep type/shape helper web stay in
Lowering; it reaches the moved collectErrorSites via self.errorAnalysis().
Lowering keeps convergeInferredErrorSets / convergeClosureShapeSets as thin pub
wrappers (the lowering pipeline + the E1.4b unit test call them); collectErrorSites
/ collectClosureShapes are deleted (no fallback). New pub: isErrorTagLiteralNode /
callTargetName / astIsPureBareInferred / astPureNamedSet / containsTag /
namedSetTags / recordClosureShape (the moved collectors / facade reach them).
lower.zig net -216 lines.
The 2 convergence unit tests (transitive SCC across a try edge; closure-shape
union) moved from lower.test.zig to error_analysis.test.zig and now drive the
facade directly; the E1.4b test stays in lower.test.zig via the wrapper. Module
named error_analysis.zig, NOT errors.zig (src/errors.zig is the DiagnosticList).
zig build, zig build test, tests/run_examples.sh (357/0) all green — no .ir churn.
