fix(A): bootstrap plumbing — init creates SSH key + known_hosts + master key (REQ-164)

Fixes UAT issues 1, 8, 9, 12C, 13:
- orca init: generates SSH keypair (GenerateOrLoadSSHKey), creates
  empty known_hosts (0600), generates master key (GenerateMasterKey +
  SaveMasterKey). All were missing from runInit — every downstream
  SSH/secrets/cluster operation failed on a fresh init.
- TOFUHostKeyCallbackPath: creates known_hosts file if it doesn't exist
  (defense-in-depth alongside init)
- Linux bootstrap: replaces buggy inline TOFU with
  proxmox.TOFUHostKeyCallbackPath (first-connect key capture works)
- --type flag help: includes "linux" (was "localhost or proxmox")
- doctor network: SSH exec probe (was HTTP /healthz to :8443 — no
  daemon in SSH-push model R-001)

---ci---
project: orca
milestone: v0.12.18
phase: A
status: complete
requirements:
  covered: [164]
---/ci---

internal/cli/init.go

@@ -6,9 +6,12 @@ import (
 	"encoding/pem"
 	"fmt"
 	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/google/uuid"
+
+	"golang.org/x/crypto/ssh"
 	"github.com/spf13/cobra"
 
 	"git.cloudinit.dev/coreci/orca/internal/acl"
@@ -16,6 +19,7 @@ import (
 	"git.cloudinit.dev/coreci/orca/internal/identity"
 	"git.cloudinit.dev/coreci/orca/internal/model"
 	"git.cloudinit.dev/coreci/orca/internal/paths"
+	"git.cloudinit.dev/coreci/orca/internal/secrets"
 	"git.cloudinit.dev/coreci/orca/internal/security"
 	"git.cloudinit.dev/coreci/orca/internal/store"
 )
@@ -59,7 +63,8 @@ func runInit(out interface{ Write([]byte) (int, error) }) error {
 		Database        string       `json:"database"`
 		CAFingerprint   string       `json:"ca_fingerprint,omitempty"`
 		CertFingerprint string       `json:"cert_fingerprint,omitempty"`
-		OS              string       `json:"os"`
+		OS              string       `json:"os"
+	"path/filepath"`
 		NodeID          string       `json:"node_id"`
 		NodeName        string       `json:"node_name"`
 		Steps           []stepResult `json:"steps"`
@@ -138,6 +143,71 @@ func runInit(out interface{ Write([]byte) (int, error) }) error {
 		}
 	}
 
+	// Step 4a: SSH keypair (idempotent — GenerateOrLoadSSHKey has a fast-path).
+	// REQ-164: without this, every sshpush.Transport dial fails because
+	// the orca SSH key doesn't exist after a fresh init.
+	sshKeyPEM, sshPubLine, err := security.GenerateOrLoadSSHKey(dir)
+	if err != nil {
+		return fmt.Errorf("generate SSH keypair: %w", err)
+	}
+	_ = sshKeyPEM
+	sshKeyFp := ""
+	if pubKey, err := ssh.ParsePublicKey(sshPubLine); err == nil {
+		sshKeyFp = ssh.FingerprintSHA256(pubKey)
+	}
+	summary.Steps = append(summary.Steps, stepResult{Label: "ssh-key", Status: "ok", Detail: sshKeyFp[:min(16, len(sshKeyFp))] + "..."})
+	if !jsonOutput {
+		fmt.Fprintf(out, "\xe2\x9c\x93 SSH keypair provisioned: fp=%s\n", sshKeyFp[:min(16, len(sshKeyFp))]+"...")
+	}
+
+	// Step 4b: known_hosts file (empty, 0600). Without this, the TOFU
+	// host-key callback fails with "no such file" on the first SSH dial
+	// (knownhosts.New requires the file to exist).
+	knownHostsPath := certpaths.KnownHostsPath()
+	if _, err := os.Stat(knownHostsPath); err != nil {
+		if os.IsNotExist(err) {
+			if err := os.WriteFile(knownHostsPath, []byte{}, 0o600); err != nil {
+				return fmt.Errorf("create known_hosts: %w", err)
+			}
+		} else {
+			return fmt.Errorf("stat known_hosts: %w", err)
+		}
+	}
+	summary.Steps = append(summary.Steps, stepResult{Label: "known-hosts", Status: "ok", Detail: knownHostsPath})
+	if !jsonOutput {
+		fmt.Fprintf(out, "\xe2\x9c\x93 Known hosts file created: %s\n", knownHostsPath)
+	}
+
+	// Step 4c: master key (32-byte random, 0600). Without this, secrets
+	// set/get/rotate and cluster seal/unseal all fail with "stat master
+	// key: no such file or directory" on a fresh init.
+	masterKeyPath := paths.MasterKeyPath()
+	if _, err := os.Stat(masterKeyPath); err != nil {
+		if os.IsNotExist(err) {
+			os.MkdirAll(filepath.Dir(masterKeyPath), 0o755)
+			masterKey, err := secrets.GenerateMasterKey()
+			if err != nil {
+				return fmt.Errorf("generate master key: %w", err)
+			}
+			if err := secrets.SaveMasterKey(masterKeyPath, masterKey); err != nil {
+				return fmt.Errorf("save master key: %w", err)
+			}
+			// Zero the key from memory (defense-in-depth, REQ-154).
+			defer secrets.ZeroKey(masterKey)
+			summary.Steps = append(summary.Steps, stepResult{Label: "master-key", Status: "ok", Detail: "generated"})
+			if !jsonOutput {
+				fmt.Fprintf(out, "\xe2\x9c\x93 Master key generated: %s\n", masterKeyPath)
+			}
+		} else {
+			return fmt.Errorf("stat master key: %w", err)
+		}
+	} else {
+		summary.Steps = append(summary.Steps, stepResult{Label: "master-key", Status: "skipped", Detail: "already present"})
+		if !jsonOutput {
+			fmt.Fprintf(out, "\xe2\x9c\x93 Master key: already present\n")
+		}
+	}
+
 	// Step 5: OS detection.
 	osDetected := detectOS()
 	summary.OS = osDetected

internal/cli/node.go

@@ -503,7 +503,7 @@ func init() {
 	nodeJoinCmd.Flags().StringVar(&joinName, "name", "", "node name (required for --type localhost)")
 	nodeJoinCmd.Flags().StringVar(&joinAddr, "addr", "", "node address (default localhost:8443)")
 	nodeJoinCmd.Flags().StringVar(&joinCAFinger, "ca-fingerprint", "", "pin CA cert SHA-256 (REQ-026); fails if on-disk CA doesn't match")
-	nodeJoinCmd.Flags().StringVar(&joinType, "type", "localhost", "node type: localhost (default) or proxmox (SSH bootstrap)")
+	nodeJoinCmd.Flags().StringVar(&joinType, "type", "localhost", "node type: localhost (default), proxmox, or linux (SSH bootstrap)")
 	nodeJoinCmd.Flags().StringVar(&joinHost, "host", "", "proxmox host address (IP/hostname, no port; required for --type proxmox)")
 	nodeJoinCmd.Flags().StringVar(&joinSSHUser, "ssh-user", "root", "SSH username for proxmox bootstrap (default root)")
 	nodeJoinCmd.Flags().StringVar(&joinSSHKey, "ssh-key", "", "SSH private key path for proxmox bootstrap (R-021: no passwords; default: orca key)")