Rules

Go runs only through docker compose run --rm <test|vet|fmt|build>; the merge gate is docker build . plus CI's changelog check.
Tests first, in their own commit; the implementation follows in the next. A re-pin of seeded output or of testdata/shipped_shape.txt is its own commit.
A change under data/ or to the shape pin adds its CHANGELOG.md entry under Unreleased in the same PR, and so does a change to a flag, an exit code, an exported name, a fence, a builtin or the lowest Go; what is major is the README's Versioning table.
One-line commit messages: no ticket prefix, no repo name, no authorship trailers.
Hard tabs. No comment by default; delete a restatement, a rationale, history, or a file preamble.
One spelling per result: reject the other at New, and let the error name the spelling to use.
A standing choice a reader would relitigate goes under Decisions in the README, not in a comment.
A README example is a json block that loads and renders as a category; readme_test.go runs every one.
Cyclomatic complexity is gated at 14: the table-shaped dispatches (linkParent, compileTemplate, renderEdges) sit at it and stay whole; a function that would pass it is decomposed.