web: XREFs, data links & extraction, ARCHIVE transmittals, worker-side saves

The last four big web-vs-desktop gaps.

XREFs: XATTACH reads the picked drawing's bytes and registers them
name-keyed (the image/PDF-underlay pattern), pre-parses on the web
worker, and the commit merge produces the same xref block flow as
native. Opened drawings resolve xrefs from the registry (trailing-name
match) before cache build; unresolved references produce ONE warning
listing the names and the fix — drop the referenced files on the page
(drops and picker opens now register their bytes) and reopen or
XRELOAD. XRELOAD works off the registry on unsaved drawings too.

Data Link & Extraction: spreadsheet links read picked xlsx/csv bytes
(calamine from slices / CSV from string) through a session registry,
so preview, refresh, and table-insert work on web; extraction takes
external drawings via a multi-file picker parsed on the worker, and
outputs CSV/TXT/.dxex via download_bytes. The disabled 'Add folder'
button explains why.

ARCHIVE/ETRANSMIT: assembles the drawing plus registered images, PDF
underlays, and session plot tables into a deterministic ZIP (minimal
writer over flate2 — no new dependency) delivered as
{stem}_transmit.zip; skipped dependencies are reported by name.

Save/autosave off the UI thread: the parse worker gains a serialize
action (protocol v5) — the document is prepared once on the main
thread (clone, styles, dimension bake), then the DWG/DXF writer pass,
the dominant cost, runs on the worker; any worker failure falls back
to inline serialization with the identical shared implementation.
The save path also clears the dirty flag only when the tab didn't
change mid-write, and the runtime-fields sidecar now carries
graphic_data, fixing a pre-existing loss of raw DWG round-trip bytes
on web-opened documents.

src/locale_catalog.rs

@@ -3153,6 +3153,7 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "XREF  Reloaded \"{}\"" => Some(("insert", "xref-reloaded")),
         "XREF  Save the drawing first to resolve relative XREF paths." => Some(("insert", "xref-save-the-drawing-first-to-resolve-relativ")),
         "XREF  Unloaded (skipped): \"{}\"" => Some(("common", "xref-unloaded-skipped")),
+        "XREF  Unresolved external references: {names} — drop the referenced DWG/DXF files on the page to register them, then reopen this drawing or run XRELOAD." => Some(("insert", "xref-unresolved-external-references")),
         "Y (mm)" => Some(("plot", "y-mm")),
         "Yards" => Some(("common", "yards")),
         "Yellow" => Some(("common", "yellow")),
@@ -3190,11 +3191,14 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "that object" => Some(("modal", "that-object")),
         "those objects" => Some(("modal", "those-objects")),
         "units" => Some(("common", "units")),
+        "{cmd}: cannot build the transmittal ZIP ({e})." => Some(("file", "cmd-cannot-build-the-transmittal-zip-e")),
         "{cmd}: cannot create folder ({e})." => Some(("file", "cmd-cannot-create-folder-e")),
+        "{cmd}: cannot package the drawing ({e})." => Some(("file", "cmd-cannot-package-the-drawing-e")),
         "{cmd}: no hatch objects." => Some(("view", "cmd-no-hatch-objects")),
         "{cmd}: no text or dimension objects." => Some(("view", "cmd-no-text-or-dimension-objects")),
         "{cmd}: not yet implemented." => Some(("view", "cmd-not-yet-implemented")),
         "{cmd}: packaged {copied} file(s) into {}" => Some(("file", "cmd-packaged-copied-file-s-into")),
+        "{cmd}: skipped {n} referenced file(s) not loaded in this session: {names}" => Some(("file", "cmd-skipped-n-referenced-file-s-not-loaded-in")),
         "{count} object(s) added to selection." => Some(("common", "count-object-s-added-to-selection")),
         "{count} object(s) pasted." => Some(("common", "count-object-s-pasted")),
         "{error}. External-change checks remain active." => Some(("file", "error-external-change-checks-remain-active")),
@@ -3543,6 +3547,9 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "Save Block As" => Some(("common", "save-block-as")),
         "Save Data Extraction" => Some(("common", "save-data-extraction")),
         "CSV" => Some(("common", "csv")),
+        "Pick the file again to load its contents in the browser." => Some(("file", "pick-the-file-again-to-load-its-contents")),
+        "Adding folders is not available in the browser. Add drawing files instead." => Some(("file", "adding-folders-is-not-available-in-the-browser")),
+        "Drawing not loaded in the browser: {name}." => Some(("file", "drawing-not-loaded-in-the-browser")),
         "Export STL" => Some(("common", "export-stl")),
         "STL Files" => Some(("common", "stl-files")),
         "Export STEP AP203" => Some(("common", "export-step-ap203")),