Add compiler-visible constrained value domains

[isomorphisms]

isomorphisms/Idric-Net now supplies the first concrete systems-library requirement for first-class value constraints.

The language needs a surface approximately equivalent to:

DestinationPort : ℕ where
  1 ≤ number
  number ≤ 65535

HTTPStatusCode : ℕ where
  100 ≤ number
  number ≤ 599

This must be more than a library wrapper. Required compiler behavior:

• reject invalid literals during elaboration;
• allow runtime parsing/checking to produce a constrained result once;
• carry exact constants such as not_found = 404 as library-declared facts;
• propagate mechanically decidable arithmetic ranges;
• refine ranges after comparisons and finite-choice cases;
• erase checking-only evidence when execution does not need it;
• preserve bounded-range / exact-value / finite-cardinality information through ANF and IR;
• let ARM/Thumb and follower backends widen only physically, without turning a finite domain into an unconstrained machine word;
• support dependent relations such as index < length and body byte length = Content-Length.

Odriç can start with the decidable subset: scalar bounds, finite cardinality, equality to constants, named-value inequalities, lengths/index bounds, and simple arithmetic range propagation.

Acceptance should use Idric-Net rather than only toy examples: 443 is a valid DestinationPort; 0 and 70000 are not; HTTP status is 100..599; not_found remains exactly 404 and 4xx; the eight-case transport result retains cardinality 8 / a three-bit semantic tag domain into backend lowering; ICU consumes the same definitions.

The design note is being added on branch language/constrained-values-idric-net as docs/constrained-values.md.