build(web): restore the wasm build — gate native-only deps off wasm

The web build had bit-rotted: native-only features added since it last
compiled pulled crates that don't build for wasm32-unknown-unknown.

- printpdf (PDF export / printing) → native-only target; the web build gets
  stub export_pdf / print_wires. It pulls a wasm-incompatible memchr 1.0.2
  via lopdf → nom_locate, and the web has no filesystem.
- getrandom 0.3 (via ahash via acadrust) → enable its wasm_js feature and add
  the matching --cfg getrandom_backend rustflag in .cargo/config.toml.
- ocs_plugin_api "host" feature (out-of-process plugin runtime: interprocess,
  libloading, memmap2, rkyv) → native-only target; the web gets the
  dependency-free manifest/ribbon contract. The host code was already
  wasm-gated; only the Cargo wiring pulled it in unconditionally.

`trunk build --release` succeeds again.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.toml

@@ -24,7 +24,9 @@ solid3d = ["dep:truck-meshalgo", "dep:truck-shapeops", "dep:lzma-sys"]
 [dependencies]
 # Stable, dependency-free add-on contract (manifest + ribbon/CadModule types).
 # Plugin authors target this crate's semver, not OpenCADStudio internals.
-ocs_plugin_api = { path = "crates/ocs_plugin_api", features = ["host"] }
+# The `host` feature (out-of-process plugin runtime: interprocess, libloading,
+# memmap2, rkyv) is native-only — see the per-target sections below; the web
+# build gets the dependency-free manifest/ribbon contract.
 # vtkio (pulled in transitively via truck-meshalgo) depends on xz2 → lzma-sys,
 # which by default links the system liblzma dynamically. On macOS that bakes a
 # Homebrew dylib path (/opt/homebrew/.../liblzma.5.dylib) into the binary, so
@@ -44,7 +46,6 @@ clap = { version = "4", features = ["derive"] }
 # Opt-in logging via --log / RUST_LOG (surfaces wgpu / iced / winit diagnostics).
 env_logger = "0.11"
 acadrust = "0.3.4"
-printpdf = "0.9.1"
 flate2 = "1"
 image = { version = "0.25", default-features = false, features = ["png", "jpeg", "bmp", "tiff"] }
 inventory = "0.3"
@@ -80,14 +81,25 @@ windows-sys = { version = "0.61", features = ["Win32_UI_Shell", "Win32_UI_Window
 acadrust = { git = "https://github.com/HakanSeven12/acadrust", branch = "main" }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+# Native enables the plugin host runtime (out-of-process plugins).
+ocs_plugin_api = { path = "crates/ocs_plugin_api", features = ["host"] }
 rayon = "1"
 open = "5"
+# PDF export / printing. Native-only: printpdf pulls a wasm-incompatible
+# `memchr` (1.0.2) via lopdf → nom_locate, and the web build has no filesystem.
+printpdf = "0.9.1"
 ureq = { version = "3", default-features = false, features = ["rustls"] }
 # Parse the GitHub Releases API response for the plugin marketplace.
 serde_json = "1"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
+# Web gets the dependency-free manifest/ribbon contract only (no plugin host).
+ocs_plugin_api = { path = "crates/ocs_plugin_api" }
 console_error_panic_hook = "0.1"
+# ahash (via acadrust) pulls getrandom 0.3, which needs the `wasm_js` backend
+# enabled to support wasm32-unknown-unknown (plus the matching rustflag in
+# .cargo/config.toml).
+getrandom = { version = "0.3", features = ["wasm_js"] }
 wasm-bindgen = "0.2"
 # fetch() returns a JS Promise; bridge it to a Rust future for the per-script
 # web font loader (#141).