feat(spec): Add client progress reporting and tool metadata

Introduce progressReporter to emit progress notifications when the client supplies a progress token. It polls playback
position (250ms), deduplicates percent updates, and is wired into Google and OpenAI TTS playback.

Enhance MCP metadata: add service and tool titles, icons, annotations, and rename implementation to mcp-tts with a
website URL.

chore(say): Validate TTS voice availability on macOS

Add voice detection and caching with IsVoiceInstalled/isLocale helpers and a user-facing VoiceNotInstalledError. Check
for installed voices in the say command and return a helpful error if a requested voice is missing. Add unit tests for
voice handling, update TTS schema (voice enum/descriptions), and adjust the integration test to use the system default
voice.

chore(openai): Set default TTS model to gpt-4o-mini-tts-2025-12-15

fix(ci): use go.mod

Update go.sum

chore: add Gemini TTS voices and CLI configs

Document the full list of Gemini voices and add config examples for Claude Desktop/Code, Codex CLI and Gemini CLI Update
Go structs and JSON schemas to include voice and model enums Expand TTS model options for Google and OpenAI and bump
deps: spf13/cobra, golang.org/x/sync, google.golang.org/genai

Update lock.go

chore: update to latest MCP Go SDK

feat: implement directory-based file locking for TTS coordination wit…

…h structured lock content

feat: implement global file locking for multi-instance TTS coordination