ipc, worker: dial and bind through netaddr (V-484)

Five hardcoded transports, three in internal/ipc and two in
internal/worker, all now go through the seam address. The unix perms
logic moved into netaddr, so the two copies of parentDir and the umask
dance are gone.

peerCaller already returned ok=false for a non-unix conn, so the
SO_PEERCRED path degrades correctly on tcp with no change.

internal/ipc/client.go

@@ -8,13 +8,15 @@ import (
 	"net"
 	"sync"
 	"time"
+
+	"github.com/kami/maven/internal/netaddr"
 )
 
-// Client — the module side of the boundary. Wraps a unix-socket connection
-// and satisfies CoreAPI, so a module imports ipc, holds a CoreAPI, and is
-// agnostic to whether it's been wired in-process (tests / daemon-embedded)
-// or over this socket (full topology). The swappability is the seam auth
-// will insert into without touching module code.
+// Client — the module side of the boundary. Wraps a connection to core and
+// satisfies CoreAPI, so a module imports ipc, holds a CoreAPI, and is
+// agnostic to whether it's been wired in-process (tests / daemon-embedded),
+// over a local unix socket, or over tcp to another host. The swappability is
+// the seam auth will insert into without touching module code.
 //
 // One Client ⇒ one conn ⇒ one concurrent request at a time. A module that
 // wants parallel requests opens one Client per goroutine; the store is the
@@ -22,7 +24,8 @@ import (
 // per-Client lock keeps frame interleaving impossible by construction.
 type Client struct {
 	conn net.Conn
-	path string // kept so a dropped conn can be re-dialed (core restart)
+	path string       // the address as configured, kept for errors and logs
+	addr netaddr.Addr // parsed, so a dropped conn can be re-dialed (core restart)
 	mu   sync.Mutex
 }
 
@@ -81,14 +84,22 @@ var readOnlyMethods = map[Method]bool{
 	MethodPing:                  true,
 }
 
-// Dial connects to a core socket at path and returns a Client. The module
-// owns its Client lifecycle; Close on shutdown.
+// Dial connects to core at path and returns a Client. The module owns its
+// Client lifecycle; Close on shutdown.
+//
+// path is a netaddr seam address: a bare path is the unix socket it has
+// always been, and "tcp://host:port?token=..." reaches a core on another
+// host. See internal/netaddr.
 func Dial(path string) (*Client, error) {
-	c, err := net.Dial("unix", path)
+	addr, err := netaddr.Parse(path)
 	if err != nil {
-		return nil, fmt.Errorf("ipc: dial %s: %w", path, err)
+		return nil, err
 	}
-	return &Client{conn: c, path: path}, nil
+	c, err := netaddr.Dial(addr)
+	if err != nil {
+		return nil, fmt.Errorf("ipc: dial %s: %w", addr, err)
+	}
+	return &Client{conn: c, path: path, addr: addr}, nil
 }
 
 func (c *Client) Close() error {
@@ -189,9 +200,9 @@ func (c *Client) call(ctx context.Context, m Method, params, result any) error {
 // re-dials clean. Caller holds c.mu.
 func (c *Client) roundtrip(m Method, raw json.RawMessage, resp *Response) error {
 	if c.conn == nil {
-		conn, err := net.Dial("unix", c.path)
+		conn, err := netaddr.Dial(c.addr)
 		if err != nil {
-			return fmt.Errorf("%w: dial %s: %v", errWriteLost, c.path, err)
+			return fmt.Errorf("%w: dial %s: %v", errWriteLost, c.addr, err)
 		}
 		c.conn = conn
 	}