Reads the variants off a drafts shelf too

[johnnyt]

Bead: sb-jc6m

What changes

The info tests that hold the graph's values to the how-to-read paragraph and the key ("names every value the hook puts after a stem" and "names every kind of mark, slot and end the graph gives", in test/statifier_blocks/map/info_test.exs) read only the two teaching documents. Neither draws a drafts shelf, so the tray slot style sat in the variants table with no graph giving it, and renaming it left the suite green.

Both tests now read their graphs through one helper, drawn_graphs/0: the two teaching documents and the loan with a drafts shelf the key tests already used (shelf_root/0). key_lines/0 reads the same helper, so the shelf document is built in one place. The kinds test now asserts the graphs give exactly the values the variants table names, so a fixture that stops drawing a variant also turns it red.

Test-only: no lib/ change, no changelog fragment (test harness, per changelog.d/README.md).

Sabotage

• Before the change, at the base: renamed the tray style to drawer in StatifierBlocks.Map's style/2 and slot_options/5 and in StatifierBlocks.Map.Info's slot/5. The info suite stayed green.
• After the change, the same rename: "names every value the hook puts after a stem" failed on its assertion (slot--${} builds a class nothing names) and "names every kind of mark, slot and end the graph gives" failed on its equality assertion. Restored from a copy, byte-equal.
• After the change: took the shelf document out of drawn_graphs/0. "names every kind of mark, slot and end the graph gives" failed on its equality assertion, the tray value missing. Restored from a copy, byte-equal.

Gate

Full mix quality green on the committed tree: format, compile, doc links, dependencies, ADR cites, docs, credo, dialyzer, and tests with 4,004 of 4,004 passed at 95.4% coverage. Doctor, gettext and sobelow are skipped as not installed.