[ASTOHACKER]

Summary

Adds a full Thai (th) interface catalog (3,596 strings, 100% full interface coverage matching Spanish, Korean and Italian) and integrates Thai font fallback and system locale detection.

• Catalog: crates/ui-egui/src/i18n/th.tsv with clean-room NLE vocabulary, matching es.tsv and ko.tsv
• Font Fallback: System font scanning in crates/ui-egui/src/cjk.rs supporting Leelawadee UI, Noto Sans Thai, Sarabun, Thonburi, etc.
• Integration: Added Language::Th in crates/ui-egui/src/i18n/mod.rs, menus.rs (Edit ▸ Language ▸ ไทย), lib.rs, and native_menu.rs
• Preferences: Engine settings test and persistence in crates/engine/src/settings.rs
• Tests & Assets: All 193 ui-egui unit tests pass; th.tsv.attribution added and cargo xtask assets passes.

[FredApps]

Requesting changes for two things I can show from the diff: a second, unrelated feature is in the branch, and the strings it adds are not in all required catalogs. The Thai catalog itself looks well put together; I can't read Thai well enough to judge the 3,596 translations, and a native reader should look at it.

1. The branch has two commits and the text describes only one. 57f394e8 is the Thai catalog, font fallback and wiring that the summary lists. d661ac76 ("ui: drag-and-drop media files from the OS file manager") is a separate feature of about 200 lines: import_mode.rs, main.rs, native_menu.rs, theme.rs and a new tests/os_drop_import_ui.rs with 149 lines. It is not mentioned in the PR text, and it has nothing to do with Thai. It also overlaps two other open PRs by the same author, #2012 ("Add Linux file-manager video drops to Source and Timeline") and #1969 (--x11 for file drag-and-drop on Linux). Please drop it from this branch; a language catalog is easier to review and to merge on its own, and the drag-and-drop work should be one PR (or one of those two).

2. Seven new strings are missing from five required catalogs. The PR adds these to es, ja and zh-cn only: no Thai font is installed on this system; the interface stays in English, Could not import the dropped files, Imported 1 file, Imported {n} files, Drop to import, Drop on the Timeline to place the clips, and the Add media to your project. Drag-and-drop needs X11 … sentence. I checked fr, id, it, ko and pt-br at this head: none of them has Drop to import or any Thai notice, and main's es.tsv does not have them either, so these are new here. Filmcraft requires es, fr, id, it, ja, ko, pt-br and zh-cn; French, Indonesian, Italian, Korean and Brazilian users get English for all seven. The Thai notice belongs to this PR's scope (the other 5 catalogs need it), and the six drop strings go with whichever PR carries that feature.

3. What I checked in the Thai catalog.

• Keys. th.tsv has 3,597 (context, source) keys against 3,590 in es.tsv on main; every es key is in th and the 7 extra are exactly the strings above, so nothing is missing and nothing is dead.
• Attribution. th.tsv.attribution and the ATTRIBUTION.md row exist in the same form as the other catalogs.
• Font gate. Thai is registered with a system-font fallback in cjk.rs (Leelawadee UI, Noto Sans Thai, Sarabun, Thonburi) and refused without a face, like Korean; I did not run it, and the tests do not render glyphs. Thai has no word spaces and needs a shaper; please attach a screenshot of the menu bar and one dialog from a real Thai face (line breaks and stacked vowels and tone marks are the usual failures).

Hosted CI does not build or test filmcraft. I have not asked for a receipt, since the strings and the branch change the head. I'll review again when they are in.