refactor(download): one blocking HTTP stack, no tokio runtime

The library is blocking end to end — vm::run waits on the machine
for the payload's whole lifetime — so the async interior bought no
concurrency (OCI layers download sequentially) and nothing any
consumer shape could use; each call rented a tokio runtime with
'Failed to create Tokio runtime' as a user-visible failure mode.
download.rs and registry.rs move to reqwest::blocking, folding the
runtime wrappers away; distro.rs joins the same client shape,
which also gives its metadata calls their first timeouts. The
shared client bounds the connect and, for small metadata bodies,
the whole request; transfers stay unbounded (the blocking client
has no per-read window; a stalled stream is the operator's
Ctrl-C). tokio and futures-util drop out as direct dependencies;
tokio remains transitively under reqwest.

Cargo.lock

@@ -362,7 +362,6 @@ dependencies = [
  "anyhow",
  "dirs",
  "flate2",
- "futures-util",
  "libc",
  "libloading",
  "log",
@@ -374,7 +373,6 @@ dependencies = [
  "tar",
  "tempfile",
  "thiserror",
- "tokio",
  "xz2",
  "zstd",
 ]
@@ -502,17 +500,6 @@ version = "0.3.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "53c0fa8157de1303bfffdaa1cc2a673bfffb60102f76b0ef4441659124373fed"
 
-[[package]]
-name = "futures-macro"
-version = "0.3.34"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9fb9654ba8355388abeb8dcb4fc62f511300867002afc858860463bdd9fe0c44"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 3.0.9",
-]
-
 [[package]]
 name = "futures-sink"
 version = "0.3.34"
@@ -533,7 +520,6 @@ checksum = "0d50a92467f8ba5dd6e3ee5d4bd04d73ab2e4e1c44474a0674821dfce14b79bc"
 dependencies = [
  "futures-core",
  "futures-io",
- "futures-macro",
  "futures-sink",
  "futures-task",
  "memchr",
@@ -1229,14 +1215,12 @@ dependencies = [
  "sync_wrapper",
  "tokio",
  "tokio-rustls",
- "tokio-util",
  "tower",
  "tower-http",
  "tower-service",
  "url",
  "wasm-bindgen",
  "wasm-bindgen-futures",
- "wasm-streams",
  "web-sys",
 ]
 
@@ -1691,21 +1675,9 @@ dependencies = [
  "mio",
  "pin-project-lite",
  "socket2",
- "tokio-macros",
  "windows-sys 0.61.2",
 ]
 
-[[package]]
-name = "tokio-macros"
-version = "2.7.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "78773a2a397f451582ce068015985c33193cf6dea8b74d2a639fe457b2f07b0e"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 3.0.9",
-]
-
 [[package]]
 name = "tokio-rustls"
 version = "0.26.6"
@@ -1947,19 +1919,6 @@ dependencies = [
  "unicode-ident",
 ]
 
-[[package]]
-name = "wasm-streams"
-version = "0.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d1ec4f6517c9e11ae630e200b2b65d193279042e28edd4a2cda233e46670bbb"
-dependencies = [
- "futures-util",
- "js-sys",
- "wasm-bindgen",
- "wasm-bindgen-futures",
- "web-sys",
-]
-
 [[package]]
 name = "web-sys"
 version = "0.3.106"