wall-identifier: classify the wall before fighting it

Project guide: the repository's AGENTS.md. If the repository has none, use AGENTS-template.md and ask the user to fill in its project adapter.

A pinned compiler is deterministic: bytes = f(preprocessed unit, flags). Retail came out of the same f from real source, so every function can be reproduced in principle; the job is finding which input differs. The unit of reproduction is the whole translation unit, because some residue is front-end state that no local edit to the body can reach. Each class below has a different lever, and two of the four are not permuter problems at all.

Start here

Using the project's tools (see the AGENTS.md adapter):

• Diff: the normalised compiled and retail pair, with the first divergence, call, branch and return counts, and both sides' leading instructions;
• Semantics: an operand, FP-opcode, constant and ordered-referent comparison;
• Switches: jump-table case-to-arm mapping against retail (a permuted table scores near-exact);
• Headroom: current versus best-ever score;
• Blocks: a basic-block view of retail;
• Referents: the actual relocation targets, unmasked.