Enable isolated Remote speech and protect reading exports

Attach incoming software speech to reader sessions with lease checks, local output priority and isolated cancellation. Preserve every document fragment source for privacy checks and export reviewed browse current-line reading, spelling and phonetic output.

Verified focused reading and Remote race tests, complete review and external Remote race suites, private relay integration, speech regressions, affected-package vet, reader build and Tentacles make check. Audible speech, physical input/Braille and live interoperability remain unverified.

internal/app/remote_speech_voice_test.go

@@ -25,6 +25,7 @@ type isolatedVoiceConnection struct {
 	write sync.Mutex
 	// The following fields belong to isolatedVoiceServer.mutex.
 	module, pending          string
+	priority                 string
 	notifications            bool
 	language, spelling, ssml string
 	voiceType, synthesis     string
@@ -34,6 +35,7 @@ type isolatedVoiceUtterance struct {
 	id                             int
 	text, language, spelling, ssml string
 	module, voiceType, synthesis   string
+	priority                       string
 }
 
 func (connection *isolatedVoiceConnection) send(message string) {
@@ -100,6 +102,8 @@ func isolated_voice_fixture(t *testing.T) (*configuredSpeaker, *isolatedVoiceSer
 						response = "251-" + connection.module + "\r\n251 OK\r\n"
 					case command == "GET VOICE_TYPE":
 						response = "251-" + connection.voiceType + "\r\n251 OK\r\n"
+					case strings.HasPrefix(command, "SET SELF PRIORITY "):
+						connection.priority = strings.TrimPrefix(command, "SET SELF PRIORITY ")
 					case strings.HasPrefix(command, "SET SELF LANGUAGE "):
 						connection.language = strings.TrimPrefix(command, "SET SELF LANGUAGE ")
 						// Server LanguageDefaultModule mappings must not silently
@@ -161,7 +165,7 @@ func isolated_voice_fixture(t *testing.T) (*configuredSpeaker, *isolatedVoiceSer
 						}
 						server.mutex.Lock()
 						connection.pending = strings.Join(lines, "\n")
-						queued = &isolatedVoiceUtterance{id: id, text: connection.pending, language: connection.language, spelling: connection.spelling, ssml: connection.ssml, module: connection.module, voiceType: connection.voiceType, synthesis: connection.synthesis}
+						queued = &isolatedVoiceUtterance{id: id, text: connection.pending, language: connection.language, spelling: connection.spelling, ssml: connection.ssml, module: connection.module, voiceType: connection.voiceType, synthesis: connection.synthesis, priority: connection.priority}
 						response = "230 OK\r\n225 QUEUED\r\n"
 						if connection.notifications {
 							response += fmt.Sprintf("701-1\r\n701-%d\r\n701 BEGIN\r\n", id)