chore: Tier 4d — hoist tempfile/criterion/half/serde to workspace.dependencies

Add [workspace.dependencies] to the root Cargo.toml for the four
duplicated-across-many-crates dependencies flagged by the earlier review:
tempfile (7 crates), criterion (6), half (4 — real version skew, clawhdf5-gpu
pinned 2.7 while others used bare 2), and serde (4). Update every consuming
crate to `dep = { workspace = true }`, preserving crate-local `optional =
true` where it already existed. half now resolves uniformly to 2.7.x
workspace-wide instead of two separate semver ranges.

Also fixed clawhdf5-filters/Cargo.toml's stale "rustyhdf5" description
while touching the file (same class of leftover rename as prior fixes).

Not touching rayon/byteorder/clap (no skew found, lower priority).

crates/clawhdf5-bench/Cargo.toml

@@ -50,9 +50,9 @@ harness = false
 clawhdf5-agent = { path = "../clawhdf5-agent" }
 clawhdf5-io = { path = "../clawhdf5-io" }
 mpi = { version = "0.8", optional = true }
-serde = { version = "1", features = ["derive"] }
+serde = { workspace = true }
 serde_json = "1"
-tempfile = "3"
+tempfile = { workspace = true }
 # Optional: libhdf5 C wrapper for side-by-side comparison (requires system libhdf5).
 # Enable with: cargo bench -p clawhdf5-bench --features libhdf5-compare
 # Uses hdf5-metno (fork of hdf5 crate) which supports HDF5 1.14.x.
@@ -60,7 +60,7 @@ hdf5 = { version = "0.12", optional = true, package = "hdf5-metno" }
 
 [dev-dependencies]
 clawhdf5 = { path = "../clawhdf5", features = ["zstd", "pcodec"] }
-criterion = { version = "0.5", features = ["html_reports"] }
+criterion = { workspace = true }
 
 [features]
 # When enabled, benchmarks add matching libhdf5 variants for side-by-side comparison.