[psyinf]

Implements TODO item 1.

What

A fan-in group can name the slots of a merge and is then matched by name, in any order:

(after: current, before: baseline) -> Compare -> verdict

Slot types can't tell two slots of the same type apart, so swapping them used to pass validation and run silently wrong. With names, the merge always receives its slots in the order it declares them.

API

• MergeStage::mergeInputNames() — override in a TypedMergeFilter / UniformMergeFilter (or hand-written) merge. mergeInputTypes() is no longer pure, so a merge can declare names only.
• registerTypedMergeFilter<Out, Ins...>(name, slotNames, merger) and registerMergeFilter<Out>(name, slotNames, combiner) overloads.
• AnyMessageFilter::mergeInputNames() (defaults to none); MergeFilter now implements MergeStage.
• dsl::StageNode::slotNames; toMermaid labels the links with slot names.

Rules

• Named group + named merge: matched by name. Unknown names (with a did-you-mean) and slots the group doesn't feed are diagnostics.
• Positional group + named merge: matched by position, as before; the names fix the slot count.
• A group names all its slots or none; naming slots of a merge that declares none is an error.
• Type mismatches name the slot: slot 'raw' of 'Merge' expects ....

Both parsers (lexy and the deprecated hand-written one) accept the syntax and still produce identical results.

Docs / tests

README (new "Named slots" section), EXAMPLE.md section 4 + textPipeline demo 3c, CHANGELOG, TODO (item removed, rest renumbered). New NamedSlotTests.cpp, plus parser-agreement cases. All 96 tests pass (MSVC debug, ASan).