## Problem
r-universe builds every package to WebAssembly (webR) in addition to the native platforms, calling `./configure --host=wasm32-unknown-emscripten`. `bindings/r/configure` only knew Linux/macOS/Windows and exited with `unsupported OS 'Emscripten'`, so the **WASM job was the single red check** on an otherwise fully-published r-universe build (all native platforms + deploy are green; the package installs fine everywhere).
## Fix
The r-universe wasm build image ships **cargo** (`/usr/local/cargo/bin`) and **emscripten** (`EMSDK` on PATH). So instead of needing a prebuilt wasm lib (which would risk an emscripten ABI/version mismatch), `configure` now detects the Emscripten host and **builds the C ABI staticlib from source** for `wasm32-unknown-emscripten` in-place — compiled with the image's own emscripten, so the ABI always matches. The static `libwickra.a` is linked into the package object (no shared lib, no rpath).
`wickra-core`'s rayon batch needs threads (absent on wasm), so the wasm build drops it via `--no-default-features`. `wickra-c` now takes `wickra-core` as a direct path dep with `default-features = false` plus a default `parallel` feature that re-enables it for native builds (a member-level `default-features = false` is ignored when inheriting a workspace dep — that was the trap).
## Validated locally
- `cargo build -p wickra-c` (default) → rayon present, builds.
- `cargo build -p wickra-c --no-default-features` (the wasm feature path) → rayon **gone**, builds.
- `cargo build --workspace`, clippy, fmt all clean; `configure` passes `sh -n`.
## Cannot be validated locally
No Rust/emscripten wasm toolchain here. The wasm build only runs in r-universe, and `configure` downloads the matching `v${version}` source tag — so this takes effect from the **first release that includes it** (the tagged source must contain the feature toggle). Open risks: whether the image has the `wasm32-unknown-emscripten` Rust target pre-installed (configure runs `rustup target add` best-effort) and the wasm build time. Worth one r-universe rebuild to confirm.
Not merging — review first.
## Problem
The R package built **only** inside the dev/CI workspace. `src/Makevars` and `configure.win` hard-required `WICKRA_INCLUDE_DIR` / `WICKRA_LIB_DIR` pointing at a pre-built `libwickra` (`configure.win` literally `: "${WICKRA_LIB_DIR:?...}"`), and there was no Unix `configure`. So **r-universe** and any plain `install.packages` / `install_github` failed — R had no working end-user install path.
## Fix
Fetch the prebuilt `wickra-c-<triple>.tar.gz` release asset matching the package version at install time and bundle the library into the package (same outcome as the C# / Java bindings, which bundle per-platform native libs):
- **New POSIX `configure`** (the Unix hook R lacked): detect OS/arch → triple, download + `untar` via **base R** (no curl/wget system dep), stage `wickra.h` + `libwickra.{so,dylib}` into `src/`, generate `src/Makevars` from `Makevars.in` with an rpath (`$ORIGIN` Linux, `@loader_path` + `install_name_tool` macOS) so the bundled lib resolves post-install.
- **`configure.win`**: drop the hard `WICKRA_LIB_DIR` requirement; download the Windows triple when unset, then keep the existing `wickra_abi.dll` rename + `objdump`/`dlltool` import-lib dance (sourcing the dll/header from the asset).
- **`install.libs.R`** also bundles `libwickra.dylib` (macOS); the `*.so`/`*.dll` globs already covered Linux/Windows.
- `WICKRA_INCLUDE_DIR`/`WICKRA_LIB_DIR` stay as an optional **dev override**.
- **CI (3 OS)** keeps building against the locally built C ABI (version-independent — avoids the chicken-egg of downloading the in-flight version) but **no longer exports `LD_LIBRARY_PATH`/`DYLD_LIBRARY_PATH`**, so it now verifies the bundled rpath — the real self-contained path users and r-universe get.
`Makevars` is now generated from `Makevars.in`; `SystemRequirements` + ignore/attributes files updated.
## Validation
- The Windows `objdump`/`dlltool` import-lib dance was smoke-tested locally against the real v0.7.9 asset (2412 `wickra_` exports → import lib built).
- Linux/macOS rpath bundling can't be tested on this Windows host → **the 3-OS `r` CI job is the gate** (now without the loader-path mask).
- Follow-up (separate, after release): set up `wickra-lib/wickra-lib.r-universe.dev` (`packages.json` → `bindings/r`).
Closes the R half of the self-contained-distribution gap (`todo-10`).
