test(setup-matrix): give each case its own home directory

run-case.sh isolated only XDG_CACHE_HOME, so every package manager it
drives resolved its cache, store and credentials from the caller's real
home. Under `setup-matrix.sh run --host` that is the developer's own
home directory.

Each case now gets HOME inside its per-case WORKDIR, along with the
variables that outrank HOME for their tools (CARGO_HOME, GOPATH,
GOMODCACHE, GOCACHE, PNPM_HOME, COREPACK_HOME, NUGET_PACKAGES and the
remaining XDG dirs). The verification helpers read through those same
variables, so they keep resolving without changes.

Author: jdalton

tests/setup_matrix/run-case.sh

@@ -664,6 +664,16 @@ export SOCKET_TELEMETRY_DISABLED=1 SOCKET_EXPERIMENTAL_MAVEN=1 SOCKET_EXPERIMENT
 # Isolate the pypi `.pth` hook's change-detection stamp per case so runs
 # don't bleed into each other (the stamp lives under XDG_CACHE_HOME).
 export XDG_CACHE_HOME="$WORKDIR/.cache"
+# Give the case its own home so every package manager's cache, store and
+# credentials stay inside WORKDIR. Under `--host` these run on the
+# developer's machine, where the default is their real home. The vars
+# below outrank HOME for their tools, so they are pointed inside it
+# rather than left to leak.
+mkdir -p "$WORKDIR/home"
+export HOME="$WORKDIR/home"
+export XDG_DATA_HOME="$WORKDIR/home/.local/share" XDG_CONFIG_HOME="$WORKDIR/home/.config" XDG_STATE_HOME="$WORKDIR/home/.local/state"
+export CARGO_HOME="$WORKDIR/home/.cargo" GOPATH="$WORKDIR/home/go" GOMODCACHE="$WORKDIR/home/go/pkg/mod" GOCACHE="$WORKDIR/home/.cache/go-build"
+export PNPM_HOME="$WORKDIR/home/.pnpm" COREPACK_HOME="$WORKDIR/home/.corepack" NUGET_PACKAGES="$WORKDIR/home/.nuget/packages"
 # NOTE: deliberately do NOT export SOCKET_CWD. The install hook's apply
 # must run with whatever cwd the package manager sets for the lifecycle
 # script — the project root for a single project, and the *member* dir