docs(justdummies): document ConstraintCall.Of's argument convention

[Reefact]

Summary

ConstraintCall.Of's second parameter takes rendered text, not parameter names, and that was only legible from the sites using it. Where the rendered text happens to spell a parameter — Distinct(comparer) — the call reads like a missing nameof, so this documents why it is a literal, on the factory that defines the rule.

Type of change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Analyzer / diagnostic change
• Tests
• Documentation
• Build / CI / tooling

Changes

• Add a <remarks> block to ConstraintCall.Of stating that arguments carries rendered text, and naming the two shapes that reach it: a value the declaring generator rendered itself (V(minimum), Join(values) → Between(0, 100)), and a word standing in for an argument that has no useful rendering, written where it reads better than the ellipsis OfElided would give (Distinct(comparer), ContainingAny(<generator>)).
• State that a stand-in is passed as the literal it is, and that nameof(...) does not belong there even when the parameter it would name happens to spell it — with the reason the rule differs from name's: a method name is a public symbol the message must follow through a rename (ADR-0065), whereas a stand-in is prose whose resemblance to a parameter is a coincidence of good naming. Tying it to the symbol would let a rename local to one overload silently reword a user-facing message, and would leave the same constraint reading differently across the generators declaring it.

No code, no diagnostic message and no test changes: the only file touched is JustDummies/ConstraintCall.cs, and only its XML documentation.

Testing

Run on the rebased branch, whose base is 574a982:

• dotnet build FirstClassErrors.sln — succeeded, 0 warnings, 0 errors
• dotnet test FirstClassErrors.sln — 2193 passed, 0 failed, 0 skipped across the 13 suites
• Analyzer tests pass (FirstClassErrors.Analyzers.UnitTests) — 132 passed, run as part of the solution test above

Documentation

• Public API / error documentation updated — the XML documentation of the internal ConstraintCall.Of factory
• README / doc/ updated
• French translation (doc/handwritten/for-users/README.fr.md) updated if user-facing behavior changed
• No documentation change required

No user-facing behavior changed, so the French user documentation is untouched.

Architecture decisions

• No architectural decision in this pull request
• New decision recorded — ADR drafted as Proposed: ADR-____
• Supersedes an existing ADR — successor proposed, status not flipped: ADR-____
• ⚠️ Conflicts with an existing ADR — flagged for the maintainer: ADR-____

This writes down the boundary of a decision already recorded rather than taking a new one: ADR-0065 ties a constraint's name to its method through nameof, and its rationale is about a public symbol surviving a rename. Nothing in it extends to the arguments, and this documents where the rule stops.

Related issues

None.