feat: in-place save (File System Access), image paste, print wiring, web capture

The last high-severity web gap plus a small integration bundle.

In-place save: with the File System Access API (Chromium/Edge), Save
now works like desktop. Plain Save on a tab with a retained handle
writes straight through — no picker, no download, no "(1)" copies.
First save or format change opens showSaveFilePicker AT the confirm
gesture (the worker serialization that follows can outlast the
transient-activation window; retained handles need no activation to
write). Picker cancel cancels the save like desktop; picker or write
failure falls back to the legacy download with a note; Firefox/Safari
keep the download flow untouched (feature-detected). Handles are
keyed by tab id in a thread-local registry (Message must be Send —
JsValue cannot ride in messages or App state); closing a tab drops
its handle; Save As re-picks. Dirty clears only on successful
persistence, same race guard as before.

Image paste: Ctrl+V of a screenshot inserts it as an image reference
— the clipboard reader falls back to image/* items when neither the
entity clipboard nor text has anything (precedence preserved), the
bytes enter the image source registry as pasted-<timestamp>.<ext>,
and attach reuses the IMAGE command's model-creation path verbatim.

Browser print: beforeprint snapshots the WebGL canvas into a print-
only <img> (the capture_canvas technique), so the browser's own print
menu produces the drawing instead of a blank page.

Automation capture on web: the capture op no longer calls the
synchronous GPU-map screenshot (dead on wasm); main's frame-parked
capture waits for a presented frame and reads via capture_canvas — the
same workaround the save-thumbnail path uses — delivering the PNG as a
download.

(cherry picked from commit 6e89b36d)

Ported onto main (#1717 review): the web capture rides main's existing
frame-parked capture (one ControlCaptureFrame path, ignoring the timer
tick on wasm) instead of a second parked-capture state; closing a tab
drops its file handle inside main's on_tab_close.

locales/ru-RU/opencadstudio.ftl

@@ -168,6 +168,8 @@ modal =
     .those-objects = эти объекты
 
 clipboard =
+    .pasted-image = Вставлено изображение "{ $name }": { $width }×{ $height } px
+    .image-unsupported = Не удалось декодировать вставленное изображение "{ $name }".
     .no-supported-content = Буфер обмена не содержит поддерживаемого текста или объектов чертежа.
     .unavailable = Системный буфер обмена недоступен.
     .occupied = Системный буфер обмена сейчас используется. Повторите попытку.
@@ -2403,6 +2405,8 @@ command =
     .tcount-placement-overwrite-prefix-suffix-overw = TCOUNT  Размещение [Заменить/Префикс/Суффикс] <Заменить>:
 
 file =
+    .in-place-save-failed-downloaded = Не удалось сохранить в файл (__ocs_fmt_0__); копия загружена
+    .save-picker-failed-downloading = Не удалось выбрать место сохранения: __ocs_fmt_0__; загружается копия
     .restore-all = Восстановить все
     .restoring-drawing-s = Восстановление __ocs_fmt_0__ чертежа(ей)…
     .session-had-open-drawing-s = В сессии было открыто __ocs_fmt_0__ чертежа(ей).