M7: Every-line Composer for ragged text

[Haven-King]

The Every-line Composer now breaks ragged (left, centre, right and auto aligned) text as well as justified text, and each text object chooses Single-line or Every-line (ParaStyle.composer, Every-line by default as in Illustrator).

What and why

Illustrator's Every-line Composer balances line breaks over the whole paragraph for ragged text too: it will move a short word down to the next line, even when it fits, to avoid a lone word on the last line and an uneven rag. VectorCraft only composed justified area text, so ragged text always broke greedily. The composer choice wasn't stored, and the Paragraph panel's composer menu items were disabled stubs.

• Model: ParaStyle.composer (vectorcraft_doc::Composer, re-exported by vectorcraft-text). It's saved only when Single-line, so older files read as Every-line. LayoutOptions.composer becomes an Option override for tests.
• Composer:
  • The justified-only gate is gone.
  • Ragged lines never shrink.
  • Badness is 100·r³, where r is the line's leftover space over a rag zone of 1/6 of the width.
  • The last line is free unless it's shorter than 1/3 of the width.
  • Hyphens cost 25 in ragged text (50 in justified).
  • Fitness classes add adjacency demerits.
  • Work is bounded: at most 4,096 active nodes, and greedy breaking above 200k glyphs.
  • Auto alignment counts as ragged.
  • A wrapped line's flush opening bracket (Mojikumi) gives its half em back to the composer.
  • Paragraphs that may hang punctuation (burasagari) keep upstream's line-by-line fallback.
• Command and UI: text.setFormat {composer: "singleLine"|"everyLine"}. The Paragraph panel menu items work and show a check mark; Reset Panel returns to Every-line.

How it was tested

• crates/text/src/tests_typo.rs:
  • every_line_composer_balances_ragged_lines: a word that greedy breaking leaves alone on the last line gets company (Every-line moves the word before it down), in left, centre, right, auto and right-to-left text, also with Standard burasagari.
  • every_line_composer_evens_the_rag: no worse than greedy on leftover space or on neighbouring line differences; every character placed.
  • single_line_composer_is_greedy.
• Command test with undo (tests_panelcmds.rs); native format round trip (native_v3.rs, and the rich_session fixture uses Single-line).
• No existing test needed changing. Upstream's mojikumi bracket test caught an interaction, which this commit fixes.
• 10k-character layout in release: ragged Every-line 5.8 ms against 4.8 ms Single-line; justified 5.6 ms.

Checklist

• cargo xtask ci passes (fmt, clippy, tests, assets, brands, layers, wasm). Run on 85aabf2: fmt, clippy, assets, brands, layers and wasm pass; the test step fails. The only failing test is cmd::typecmd::area_tests::leading_model_is_set_per_paragraph_and_saved_only_when_top_to_top, an upstream test that fails the same way on main (it depends on the machine's CJK font).
• No panics in shipped code: no unwrap(), expect(), panic!, unreachable!, todo! or
  unimplemented! outside tests, and no unchecked indexing on data from files, parameters or
  messages. Errors are returned as Result and shown to the user
  (why and how). Clippy's no-panic lints pass on 85aabf2.
• Clean-room: nothing copied from Adobe products or GPL/AGPL code (AGENTS.md).
• Every new asset has a row in ASSETS.md (no new assets).

[bflatastic]

Merged, thank you @Haven-King! The Every-line Composer for ragged text is a real typographic upgrade. The rag-zone badness, the free-unless-short last line, cheaper hyphens in ragged text and fitness-class demerits are all sensible choices, the work bound and greedy fallback keep it safe on huge paragraphs, and the Paragraph panel's composer items finally do something.

I checked it with the CLI: a 14 pt left-aligned paragraph at 150 pt wide breaks into a visibly more even rag than Single-line, and at other widths both agree. One thing I flagged in the landing notes: since a missing composer reads as Every-line, ragged text in existing files may reflow when reopened. That's fine at this stage, and it matches Illustrator's default.