ci(wasm): bump trunk-action v0.5.0 -> v0.5.1 for aarch64

`Install Trunk` has never run to completion here, because the two steps
before it always failed first. With those cleared it becomes reachable,
and on this runner v0.5.0 would fetch the wrong binary.

v0.5.0 switches on PLATFORM alone and never consults the architecture:

  case 'linux': arch = 'x86_64-unknown-linux-gnu'; break;

v0.5.1 reads it and maps it, failing loudly rather than wrongly:

  const arch = process.env['ARCH'] || process.arch;
  case 'x64':   targetArch = 'x86_64';  break;
  case 'arm64': targetArch = 'aarch64'; break;
  default: core.setFailed(`Unsupported architecture: ${arch}`); return;

Node reports `arm64` here, so it resolves to `aarch64`, and upstream does
publish trunk-aarch64-unknown-linux-gnu.tar.gz. There is also an `ARCH`
env override if the mapping is ever wrong.

Read out of the two bundled dist/index.js files, not the release notes.
Counts moved as predicted: `x86_64-unknown-linux-gnu` 1 -> 0, `aarch64`
0 -> 1, `os.arch()` 5 -> 5. Confirmed independently on both machines.

Two further changes the bump carries, neither of them about architecture:

  * the download host moves thedodd/trunk -> trunk-rs/trunk. Trunk moved
    repositories and v0.5.0 still points at the old one -- arguably the
    more durable half of the fix.
  * `io.mv` 1 -> 0 and `io.cp` 2 -> 3. A cross-filesystem move throws
    EXDEV; a copy does not. This is the fix for self-hosted runners whose
    /tmp is a separate filesystem, which is ours. NOTE: the string EXDEV
    appears zero times in either bundle, so this cannot be found by
    grepping for the error it prevents -- it is visible only as the
    primitive swap.

STILL UNVERIFIED: whether `trunk build --release` then succeeds. Everything
above concerns selecting and fetching the binary. The step after it has
never run in this repository's history, on any architecture, so there is no
basis to predict it. Expect to read that log fresh.

Refs #11

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -111,7 +111,16 @@ jobs:
         uses: Swatinem/rust-cache@v2
 
       - name: Install Trunk
-        uses: jetli/trunk-action@v0.5.0
+        # v0.5.0 selects the download by PLATFORM ONLY and never consults the
+        # architecture -- `case 'linux': arch = 'x86_64-unknown-linux-gnu'` --
+        # so on this aarch64 runner it fetches an x86_64 binary. v0.5.1 adds
+        # `process.arch` with 'x64' -> 'x86_64', 'arm64' -> 'aarch64' and
+        # core.setFailed otherwise, so a wrong arch now fails loudly instead of
+        # silently. It also moves the download host thedodd/trunk ->
+        # trunk-rs/trunk (trunk moved repositories; v0.5.0 still points at the
+        # old one), and swaps io.mv for io.cp, which is what avoids EXDEV on a
+        # self-hosted runner whose /tmp is a separate filesystem -- ours.
+        uses: jetli/trunk-action@v0.5.1
 
       - name: Check WASM compile
         run: >