claude: use the glibc Linux build, not musl (#15)

## What

Switch the `claude` plugin's Linux download from the `musl` build to the
glibc build (`linux-{arch}/claude`).

## Why

The upstream `linux-x64-musl` binary is **not static**: it is
dynamically linked against `/lib/ld-musl-x86_64.so.1`. On a glibc host
(e.g. the `ubuntu-24.04` CI runners) that loader is absent, so executing
it fails with `No such file or directory (os error 2)` (ENOENT from the
missing interpreter).

This surfaced when
[claude-marketplace#1](Genesis-Embodied-AI/claude-marketplace#1)
CI ran `proto run claude -- plugin validate` on ubuntu and failed even
though install succeeded.

```
$ file linux-x64-musl/claude → interpreter /lib/ld-musl-x86_64.so.1   # fails on glibc
$ file linux-x64/claude      → interpreter /lib64/ld-linux-x86-64.so.2 # runs on ubuntu
```

The glibc build runs on standard Linux distros and CI. (The musl build
remains the right choice only on musl/Alpine hosts, which this repo's CI
and consumers are not.)

## Note on the smoke test

`scripts/smoke-test.sh` did not catch this: it asserts `proto bin
claude` is a `-x` file but never executes it, so a binary built for the
wrong libc still passes. The original
[#14](#14) CI
was green for that reason.

Linear: PLAT-1014

Author: etiennecoutaud

claude/README.md

@@ -24,7 +24,8 @@ also published at
 ## Notes
 
 - Binaries are served from `https://downloads.claude.ai/claude-code-releases/`
-  as a single executable per platform (no archive). Linux uses the static
-  `musl` build so it runs on both glibc and musl hosts.
+  as a single executable per platform (no archive). Linux uses the glibc build:
+  the upstream `musl` variant is dynamically linked against the musl loader (not
+  static), so it fails on glibc hosts such as standard CI runners.
 - Upstream publishes checksums only inside a per-version `manifest.json`, which
   the TOML plugin format cannot parse, so installs are not checksum-verified.

claude/plugin.toml

@@ -9,12 +9,14 @@ aarch64 = "arm64"
 x86_64 = "x64"
 
 # Claude Code ships a single prebuilt binary per platform (no archive), served
-# from downloads.claude.ai under a {version}/{platform}/<binary> path. The Linux
-# build uses the static musl variant so it runs on both glibc and musl hosts.
+# from downloads.claude.ai under a {version}/{platform}/<binary> path. Linux uses
+# the glibc build: the upstream "musl" variant is not static (it is dynamically
+# linked against /lib/ld-musl-x86_64.so.1), so it fails with ENOENT on glibc hosts
+# such as the ubuntu CI runners; the glibc build runs on standard Linux and CI.
 # Per-version checksums exist only inside a manifest.json (keyed JSON), which the
 # TOML plugin format cannot parse, so no checksum-url is published here.
 [platform.linux]
-download-file = "linux-{arch}-musl/claude"
+download-file = "linux-{arch}/claude"
 exe-path = "claude"
 
 [platform.macos]