Type: the Every-line Composer composes paragraphs that mix type sizes in rectangular area type

A paragraph with one character in a different type size was broken
with the Single-line Composer, even when Every-line was chosen: the
composer gave up whenever the paragraph's glyphs did not all have the
same line metrics (ascent, descent, leading, cap height, x height and
em box top).

In rectangular area type without text wrap, rows and columns included,
the width of a line does not depend on how far down the frame it is.
There the Every-line Composer now composes a paragraph whose
characters differ in line metrics (type size, font, leading or
vertical scale, or an inline graphic taller than the text), and each
line takes its height from its own text, as with the Single-line
Composer. Area type of another shape, or with text wrap, still breaks
such a paragraph with the Single-line Composer.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -4441,7 +4441,9 @@ when it is Single-line). Every-line, the default, picks the breaks of the whole
 justified text gets even word spacing, ragged text (left, centre or right aligned) an even rag, so it may move a word
 that fits to the next line to avoid a lone short word on the last line or a full line next to a short one.
 Single-line fills each line as far as it goes. Point type and type on a path have no line width, so both composers
-give the same result there; paragraphs that mix type sizes fall back to Single-line.
+give the same result there. A paragraph whose characters differ in line metrics (type size, font, leading or vertical
+scale, or an inline graphic taller than the text) is composed with Every-line in rectangular area type, rows and
+columns included; in area type of another shape, or with text wrap, it falls back to Single-line.
 
 ```json
 {"name":"run_command","arguments":{"command":"text.setFormat","params":{"ids":[7],"composer":"singleLine"}}}