#8882 Draw commit records as semantic diffs of the compiler's objects

A pure module, with no file system and no git: it parses a record (sections, change blocks, git trailers) and draws it as HTML. Each kind of object has its drawing: a typing rule as an inference rule, an AST or typed tree fragment as a tree, a clause matrix as a matrix, Lambda and JavaScript as highlighted code with Before and After side by side, a runtime representation as ReScript ↦ JavaScript lines, a diagnostic as its text. The kinds are a typed table, so a kind without a drawing does not type-check. A modified block's two versions of code, a tree or text are drawn as aligned rows: a line both have faces itself, the changed lines between are padded with gaps, and on a narrow screen the rows read as a unified diff. An added or removed block's one version spans the block. A long line wraps, its continuation indented past the line's own indentation or tree connectors. It checks each record against its diff: changelog fragments, the required trailers, the Tests trailer against the test files both ways (every listed path is in the diff; every test file in the diff other than a generated snapshot is listed, the missing ones named), generated JavaScript against Output, magic numbers, the v0 PPX bridge, super_errors fixtures and tests/ERROR_VARIANTS.md.

Reads each commit's record, files, magic-number diff and changes/ fragments from git and hands them to recordRender.js, which parses, checks and draws them. Its options are --out, --pr, --title and --fragment.

Prints, for one example and one compiler build, the parser's tree, the tree after the built-in PPX, the JSX transform's output, the formatter's output, the typed tree, the inferred interface, Lambda as translated and after each pass that changes it, the generated ES module and the diagnostic, each as the compiler prints it, under a line naming the compiler and the commit its checkout is at. Run with --bsc on a build of the parent commit, it gives a modified block's Before.

Refuses a message without the Area, Output, Tests and Signed-off-by trailers, with a trailer after Signed-off-by, or with a malformed Output or Tests; for a commit that changes compiler, runtime, build system or editor tooling sources, also one without Why: or a change block.