fix(step-recorder): a composer, a slider and seven ARIA roles now record a step

[gololdf1sh]

Part of #111 — three of its five gaps. The masked-retry gap (D12) and the pill's "values off"
chip follow in a second pull request, which is the one that closes the issue.

Each gap ends the same way for the tester: they act, the counter does not move, and the saved
test is missing a step.

What now records

• A composer. isContentEditable makes an element a text field whose value is its own text,
  so a comment box, a CMS body and a chat composer record like any input. The click on the
  composer stays dropped — it is focus noise the Type step absorbs, exactly as for an input.
• A slider, a colour and a file picker. One change branch each. Set the "Volume" slider to "7", Set the "Colour" picker to "#ff0000", Attach "photo.png" to the "Avatar" field — the
  filename from files[0].name, falling back to the last segment of the C:\fakepath\… value.
  The never-values toggle is their only rule: a slider position is not a secret and a filename is
  not one either. Under it they say Set the "Volume" slider and Attach a file to the "Avatar" field, and hand the editor a withheld-value marker rather than an empty string.
• Seven ARIA roles in CLICK_SEL: link, combobox, listbox, slider, spinbutton, treeitem,
  gridcell — each with the verb a tester would write by hand (Open the "Country" dropdown,
  Select "Payments" in the tree) instead of falling back to "the button".

RecMask.maskedAs takes the entered value as an argument now: a composer has no .value, and
without this a card number typed into one would be recorded verbatim. That row is D19b.

Two holes closed on the way

• A file input the page clears (its own Remove button) fires change with nothing chosen and
  wrote Attach "" to the field. It now records nothing — D18d.
• A muted slider handed the editor value: "" (masked). It now says a value existed and was
  withheld — D18c.

Turned on

A26, D18 and D19 were deferred with test.todo naming this issue; they are live rows now.
A27 (all seven role sentences, named and nameless), D18b, D18c, D18d, D19b and M66
are new. tests/helpers/mini-dom.mjs learned isContentEditable — inherited, nearest statement
wins — because D19 cannot run without it.

node --test tests/*.test.mjs — 411 tests, 391 pass, 0 fail, 20 todo. Against pre-fix copies
through REC_SRC / REC_MODULES every new row fails, and with only rec-mask.js swapped back
D19b alone fails.

Known, unchanged

In a multi-line composer each Enter writes its own step carrying the whole text so far. A
<textarea> already behaves that way; suppressing it would lose the step in a chat, where Enter
sends the message and empties the box.

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