Fonts: use craft-fonts as an optional build input; move the Japanese fonts out

The Japanese fonts (BIZ UDPGothic Regular/Bold for the UI, BIZ UDMincho for text
watermarks; #110, #114) now come from storytold/craft-fonts instead of assets/fonts/.

- crates/engine/build.rs: the craft-fonts recipe. With CRAFT_FONTS_DIR set it embeds
  the manifest's fonts as lightcraft_engine::CRAFT_FONTS (wasm32: BIZ UDPGothic Regular
  only, for the web size budget); unset, CRAFT_FONTS is empty. Local files only, no
  network; craft-fonts is not in any Cargo.toml.
- UI: theme::font_definitions adds the Japanese faces after Inter and egui's defaults
  in every family (BIZ UDPGothic first, Bold first for semibold). About box lists the
  embedded families.
- Watermarks: Inter, then the craft-fonts Japanese faces (Mincho first).
- Removed BIZUDPGothic-Regular/Bold.ttf, BIZUDMincho-Regular.ttf and their OFL files,
  and their ATTRIBUTION rows; added an attribution row for craft-fonts as an optional
  build input; NOTICE updated.
- Tests: Japanese glyph tests use CRAFT_FONTS and skip without it; new tests for
  Japanese in the UI with craft-fonts and for the UI and watermarks without it.
- CI: the FreeBSD job builds/tests with craft-fonts. Releases check out craft-fonts at
  a pinned commit, build with CRAFT_FONTS_DIR + CRAFT_FONTS_REQUIRED=1, and ship the
  fonts' OFL licences (plus NOTICE) in every package.
- Docs: AGENTS.md, CLAUDE.md, README, docs/web.md, docs/localization-ja.md, ROADMAP,
  parity.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/localization-ja.md

@@ -5,7 +5,10 @@ LightCraft は日本語と英語（English）の表示に対応しています
 
 - 「編集 → 言語」または「設定 → 一般 → 言語」で日本語とEnglishを切り替えます。選択は次回起動にも引き継ぎます。
 - メニュー、写真編集、マスク、切り抜き、設定、読み込み、書き出し、主な処理状況を翻訳しています。
-- 通常表示と太字の双方に、SIL OFLのBIZ UDPGothicを組み込みました。
+- 通常表示と太字の双方に、SIL OFLのBIZ UDPGothicを使います。日本語フォントはこのリポジトリではなく
+  [storytold/craft-fonts](https://github.com/storytold/craft-fonts) にあり、任意のビルド入力
+  `CRAFT_FONTS_DIR=../craft-fonts` を指定したビルド（公式リリースはすべて）に組み込まれます。
+  指定しない場合も動作しますが、日本語の文字は表示されません。
 - 翻訳は表示層で行います。操作コマンドのID、写真のファイル名、入力したメタデータを変更しません。
 - 翻訳されていない技術的なエラー、追加情報、リリースノートは英語で表示します。
 
@@ -18,4 +21,4 @@ LightCraft は日本語と英語（English）の表示に対応しています
 `LIGHTCRAFT_LANGUAGE=ja lightcraft-cli snapshot ...` で日本語の画面を描画できます。
 
 表示・フォント・言語の切り替え・設定の保存・コマンドIDの保持は
-`cargo test -p lightcraft-ui-egui i18n::tests` で検証します。
+`cargo test -p lightcraft-ui-egui i18n::tests` で検証します（グリフの検査は `CRAFT_FONTS_DIR` 指定時のみ実行）。

docs/parity.md

@@ -797,7 +797,7 @@ From `08-lightroom-classic-extras.md` (Classic-only features) and part 2 of `06-
 ### Japanese text watermarks
 
 `app.export` watermark objects accept `vertical` (boolean, defaults to false). The export
-dialog offers Horizontal/Vertical and multiline text. Japanese glyphs fall back to bundled
-BIZ UDMincho. Vertical lettering uses upright em cells and right-to-left newline columns;
+dialog offers Horizontal/Vertical and multiline text. Japanese glyphs fall back to the craft-fonts
+Mincho faces (BIZ UDMincho; on the web build, BIZ UDPGothic) when built with `CRAFT_FONTS_DIR`. Vertical lettering uses upright em cells and right-to-left newline columns;
 Latin stays upright. Advanced Japanese composition remains open. Regression coverage:
-`export::tests::japanese_watermarks_support_vertical_columns_and_legacy_defaults`.
+`export::tests::japanese_watermarks_support_vertical_columns`, `japanese_watermark_options_and_legacy_defaults`, `watermarks_work_without_craft_fonts`.

docs/web.md

@@ -52,6 +52,14 @@ codecs) at opt-level 3 and the rest (egui, eframe, serde, glue) at "s". What goe
 is the brotli column: 3.1 MB, 11 % less than the old build's brotli size and 41 % less than its
 gzip size (5.25 MB). `wasm-opt -Oz`, when installed, shrinks it further.
 
+**Fonts.** The browser has no system fonts to fall back on, so Japanese text comes from
+[craft-fonts](https://github.com/storytold/craft-fonts), the optional `CRAFT_FONTS_DIR` build
+input (`CRAFT_FONTS_DIR=../craft-fonts cargo xtask web`; release builds always set it). On wasm32
+`crates/engine/build.rs` embeds only BIZ UDPGothic Regular (UI, and the watermark fallback), so
+the module stays well under Cloudflare's 25 MiB per-file limit: measured 2026-10-06, 17.1 MB
+without craft-fonts and 21.8 MB with it (brotli 3.8 MB / 6.3 MB). Without it the web build
+works, but Japanese text has no glyphs.
+
 ## Deploying: headers
 
 `cargo xtask web --serve` sends these on every response. A production server may send them too;