fix(membership): register directory route as /directory, not /api/directory

Caddy strips /api via `handle_path /api/*` before forwarding to membershipd,
so the SPA's GET /api/directory arrives as GET /directory. The route was
registered with the /api prefix, so the stripped request hit no route and
returned 404 in production: the directory never resolved and uniweb fell back
to short ids. Every other control-plane route is registered without the prefix;
this aligns directory with them.

The unit test passed despite the bug because it requested /api/directory, the
same wrong path as the registration. Corrected the request paths to /directory
so the test now exercises the real production path (verified: reverting the
registration to /api/directory now makes TestDirectoryGolden fail with 404).

Bump 0.15.0 -> 0.15.1.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pkg/membership/server.go

@@ -420,7 +420,10 @@ func (s *Server) routes() {
 	// names instead of raw endpoint hashes. Unlike /users it is NOT admin-only and
 	// returns only active users; under enforce the auth middleware already rejects
 	// an unauthenticated caller with 401 before this handler runs (uniweb/0002).
-	s.mux.HandleFunc("GET /api/directory", s.handleDirectory)
+	// Registered without the /api prefix like every other control-plane route:
+	// Caddy strips /api via handle_path /api/* before forwarding to membershipd,
+	// so the SPA's GET /api/directory arrives here as GET /directory.
+	s.mux.HandleFunc("GET /directory", s.handleDirectory)
 }
 
 // ---- wire types -----------------------------------------------------------
@@ -519,7 +522,7 @@ type addUserReq struct {
 	Role    string `json:"role"`
 }
 
-// directoryMember is one entry of the GET /api/directory response: enough for a
+// directoryMember is one entry of the GET /directory response: enough for a
 // client to map a message's endpoint id (which the bus stamps on every frame)
 // back to a readable handle. endpoint is derived server-side from sign_pub with
 // the SAME construction the bus uses (frame.EndpointID = base64url(sha256(signPub)),
@@ -531,7 +534,7 @@ type directoryMember struct {
 	Role     string `json:"role"`
 }
 
-// directoryResp is the GET /api/directory response envelope. The members key is a
+// directoryResp is the GET /directory response envelope. The members key is a
 // stable contract consumed by the browser client; do not rename it.
 type directoryResp struct {
 	Members []directoryMember `json:"members"`