fix(P1): set Go env vars in ci-run.sh — shell-isolated executor drops them

CoreCI's buildIsolatedEnv does NOT forward GOROOT, GOPATH, GOCACHE,
GOMODCACHE (they're in the systemVars deny-list in pass_through.go).
The shell-isolated executor's env only has PATH, HOME, LANG, TMPDIR,
TERM, CI + CORECI_* + CI_* + job vars. Without GOMODCACHE/GOCACHE, Go
commands fail (can't find module/build cache). Fix: re-derive them from
the go binary on PATH via 'go env GOROOT' etc.

---ci---
project: orca
phase: 1
milestone: v0.16
status: execute
---/ci---

scripts/ci-run.sh

@@ -19,6 +19,17 @@ if [ -z "$JOB" ]; then
   exit 1
 fi
 
+# CoreCI's shell-isolated executor (buildIsolatedEnv) does NOT forward
+# Go toolchain env vars (GOROOT, GOPATH, GOCACHE, GOMODCACHE are in the
+# systemVars deny-list). Re-derive them from the `go` binary on PATH so
+# Go commands work in the shell-isolated executor.
+if command -v go >/dev/null 2>&1; then
+  export GOROOT="${GOROOT:-$(go env GOROOT)}"
+  export GOPATH="${GOPATH:-$(go env GOPATH)}"
+  export GOCACHE="${GOCACHE:-$(go env GOCACHE)}"
+  export GOMODCACHE="${GOMODCACHE:-$(go env GOMODCACHE)}"
+fi
+
 info() { echo "ci-run: $*"; }
 err()  { echo "ci-run: error: $*" >&2; exit 1; }