web: raster images, WBLOCK/SAVEALL/SCRIPT/CTB/LAYTRANS/INSERT, filled TTF text

A fresh web-vs-desktop audit found the remaining gaps; this closes the
top ten.

Raster images: IMAGE attach read the picked file via image::open on a
name-only path (dead on wasm), and raster references inside opened
drawings decoded the same way. Picked bytes are now registered in a
name-keyed store (the PDF-underlay pattern), decoding runs from memory,
and dropped .png/.jpg/.bmp/.tif files register by name so unresolved
references in opened drawings re-resolve and render (and export to PDF).

Command gaps fixed with the bytes-at-pick / download_bytes pattern:
- WBLOCK now downloads the extracted block instead of failing on fs.
- SAVEALL saves every dirty tab instead of printing a no-op message.
- SCRIPT picks and reads the .scr file through the browser picker.
- CENTERLTYPEFILE picks the .lin/.dnl file and populates from text.
- Custom .ctb tables picked on web now parse, register for the
  session, appear in the plot dialog list, and apply (load_named
  previously returned builtin-only on wasm).
- LAYTRANS 'Load standards file' parses the picked drawing on the
  existing web worker.
- INSERT 'from file' in the block palette parses picked bytes and
  feeds the shared import path.

Text fidelity: TTF-named styles rendered as thin stroke glyphs on web
because the font database was empty. Fetched Noto faces are now
registered into it with a family alias table (Arial, Times New Roman,
Cambria, ... -> Noto Sans/Serif), so those styles render filled, shape,
export to PDF as vector fills, and appear in the style picker.
ViewCube labels request semibold again on web.

docs/native-vs-web.md: the hatch and font rows were stale (both work on
web now), the GPU row claimed WebGPU is used where available (the
backend is pinned to OpenGL), and the parallelism row missed the parse
worker — all corrected.

src/app/mod.rs

@@ -2191,6 +2191,19 @@ pub enum Message {
     LayerTranslatorLoad,
     /// A target set was read from `path`.
     LayerTranslatorLoaded(std::path::PathBuf),
+    /// Web: a standards drawing picked and parsed in the browser, with the
+    /// target layers already extracted — a name-only path has nothing behind
+    /// it for `load_targets` to read. `Ok(None)` = cancelled.
+    #[cfg(target_arch = "wasm32")]
+    LayerTranslatorLoadedWeb(
+        Result<
+            Option<(
+                String,
+                Vec<crate::modules::draw::layers::laytrans::TargetLayer>,
+            )>,
+            String,
+        >,
+    ),
     LayerTranslatorSelectFrom(String),
     LayerTranslatorSelectTo(String),
     /// Pair the two selected layers.
@@ -2321,6 +2334,14 @@ pub enum Message {
     /// dispatch, this accepts an interactive verb and all of its arguments on
     /// the same line (`BOX 0,0,0 10,10,0 10`).
     ScriptLine(String),
+    /// Web SCRIPT: the picked .scr file's name and text. `None` = the
+    /// browser dialog was cancelled.
+    #[cfg(target_arch = "wasm32")]
+    ScriptFilePicked(Option<(String, String)>),
+    /// Web CENTERLTYPEFILE: the picked .lin/.dnl file's name and text.
+    /// `None` = cancelled.
+    #[cfg(target_arch = "wasm32")]
+    CenterlineLinetypeFilePicked(Option<(String, String)>),
     /// Append one typed character to the command-line input from the
     /// global key-press subscription. Used when the text-input widget
     /// itself isn't focused (focus parked on viewport / button / etc.)