feat(P01): CLI skeleton with Cobra, subcommand stubs, pre-push hook

Implements Phase 1 of v0.1 Foundation:
- go.mod with Go 1.25
- cmd/orca/main.go entry point
- internal/cli/root.go with global --json flag
- internal/cli/version.go (orca version)
- internal/cli/init.go (orca init - creates ~/.orca/)
- internal/cli/status.go (orca status - shows daemon info)
- internal/cli/node.go (orca node {join,leave,list} - stubs)
- internal/cli/job.go (orca job {run,list,stop,logs} - stubs)
- Makefile (build, test, lint, fmt, release)
- LICENSE (MIT)
- README.md with quickstart
- .gitignore
- .githooks/pre-push + scripts/trigger_coreci.sh (CoreCI trigger)
- Smoke tests in internal/cli/root_test.go

Verified: go build, go test, go vet, gofmt all pass.

---ci---
project: orca
phase: 1
milestone: v0.1
status: execute
req_covered:
  - REQ-001
  - REQ-002
  - REQ-013
  - REQ-015
  - REQ-016
  - REQ-019
  - REQ-024
---/ci---

internal/cli/node.go

@@ -0,0 +1,45 @@
+package cli
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var nodeCmd = &cobra.Command{
+	Use:   "node",
+	Short: "Manage orca nodes",
+	Long:  "Join, leave, or list orca nodes in the cluster.",
+}
+
+var nodeJoinCmd = &cobra.Command{
+	Use:   "join",
+	Short: "Join a node to the orca cluster",
+	Long:  "Register the local node with the orca cluster. Implemented in Phase 2.",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return notImplemented("orca node join")
+	},
+}
+
+var nodeLeaveCmd = &cobra.Command{
+	Use:   "leave",
+	Short: "Remove a node from the orca cluster",
+	Long:  "Deregister a node from the orca cluster. Implemented in Phase 2.",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return notImplemented("orca node leave")
+	},
+}
+
+var nodeListCmd = &cobra.Command{
+	Use:   "list",
+	Short: "List all nodes in the orca cluster",
+	Long:  "Display all registered nodes. Implemented in Phase 2.",
+	RunE: func(cmd *cobra.Command, args []string) error {
+		return notImplemented("orca node list")
+	},
+}
+
+func init() {
+	nodeCmd.AddCommand(nodeJoinCmd)
+	nodeCmd.AddCommand(nodeLeaveCmd)
+	nodeCmd.AddCommand(nodeListCmd)
+	rootCmd.AddCommand(nodeCmd)
+}