StringPlan

spirv-unified-lowering `SUP-48` — how a string-typed result is produced, when it is not produced by compiling anything.

In the namespace expredit. Declared in src/libs/libexpredit/expredit/ExprTypes.hpp.

Detailed description

SPIR-V has no string type and this spec deletes the only front end that could compile one, so a string reference is **routed around the compiler** (owner decision, §SUS-6). The whole expressible surface is *bind a string, select a string, read a string* (§SUS-5), which is a substitution and needs no parser.

**Exactly two kinds, and that is a stated limit rather than an accident.** §SUS-6d fixes the trigger for revisiting the decision: *if the recognizer needs a third node kind, it stops being a recognizer* and a dedicated substitution evaluator becomes the cheaper answer. Adding `Kind::` here is therefore a signal to re-read that paragraph, not a routine extension.