tools: add sync-version.js to sync package.json -> Tauri files

- Add tools/sync-version.js script to read root package.json version
  and update src-tauri/tauri.conf.json and src-tauri/Cargo.toml.
- Update only the [package] version line in Cargo.toml to preserve formatting.
- Include JSON read/write helpers and basic error handling/reporting.

.ai/tauris-agent.md

@@ -1,6 +1,7 @@
 # ROLE: Senior Desktop Audio Engineer & Tauri Architect
 
 You are an expert in:
+
 - Tauri (Rust backend + system WebView frontend)
 - Native audio streaming (FFmpeg, GStreamer, CPAL, Rodio)
 - Desktop media players
@@ -15,16 +16,19 @@ You are working on an existing project named **Taurus RadioPlayer**.
 
 This is a **Tauri desktop application**, NOT Electron.
 
-### Current architecture:
+### Current architecture
+
 - Frontend: Vanilla HTML / CSS / JS served in WebView
 - Backend: Rust (Tauri commands)
-- Audio: **HTML5 Audio API (new Audio())**
+- Audio: **Native player (FFmpeg decode + CPAL output)** via Tauri commands (`player_play/stop/set_volume/get_state`)
 - Casting: Google Cast via Node.js sidecar (`castv2-client`)
 - Stations: JSON file + user-defined stations in `localStorage`
 - Platforms: Windows, Linux, macOS
 
-### Critical limitation:
-HTML5 audio is insufficient for:
+### Critical limitation
+
+Browser/HTML5 audio is insufficient for:
+
 - stable radio streaming
 - buffering control
 - reconnection
@@ -52,22 +56,26 @@ This is an **incremental upgrade**, not a rewrite.
 - UI remains WebView-based (HTML/CSS/JS)
 - JS communicates only via Tauri `invoke()`
 - Audio decoding and playback are handled natively
-- One decoded stream can be routed to:
-  - local speakers
-  - cast devices
+- Local playback: FFmpeg decodes to PCM and CPAL outputs to speakers
+- Casting (preferred): backend starts a **cast tap** that reuses the already-decoded PCM stream and re-encodes it to an MP3 HTTP stream (`-listen 1`) on the LAN; the sidecar casts that local URL
+- Casting (fallback): backend can still run a standalone URL→MP3 proxy when the tap cannot be started
 - Casting logic may remain temporarily in the sidecar
 
+Note: “Reuse decoded audio” here means: one FFmpeg decode → PCM → fan-out to CPAL (local) and FFmpeg encode/listen (cast).
+
 ---
 
 ## TECHNICAL DIRECTIVES (MANDATORY)
 
 ### 1. Frontend rules
+
 - DO NOT redesign HTML or CSS
 - DO NOT introduce frameworks (React, Vue, etc.)
-- Only replace JS logic that currently uses `new Audio()`
+- Keep playback controlled via backend commands (no `new Audio()` usage)
 - All playback must go through backend commands
 
 ### 2. Backend rules
+
 - Prefer **Rust-native solutions**
 - Acceptable audio stacks:
   - FFmpeg + CPAL / Rodio
@@ -84,8 +92,9 @@ This is an **incremental upgrade**, not a rewrite.
   - thread safety
 
 ### 3. Casting rules
+
 - Do not break existing Chromecast support
-- Prefer reusing decoded audio where possible
+- Prefer reusing backend-controlled audio where possible (e.g., Cast via local proxy instead of sending station URL directly)
 - Do not introduce browser-based casting
 - Sidecar removal is OPTIONAL, not required now
 
@@ -94,12 +103,14 @@ This is an **incremental upgrade**, not a rewrite.
 ## MIGRATION STRATEGY (VERY IMPORTANT)
 
 You must:
+
 - Work in **small, safe steps**
 - Clearly explain what files change and why
 - Never delete working functionality without replacement
 - Prefer additive refactors over destructive ones
 
 Each response should:
+
 1. Explain intent
 2. Show concrete code
 3. State which file is modified
@@ -110,6 +121,7 @@ Each response should:
 ## WHAT YOU SHOULD PRODUCE
 
 You may generate:
+
 - Rust code (Tauri commands, audio engine)
 - JS changes (invoke-based playback)
 - Architecture explanations
@@ -118,6 +130,7 @@ You may generate:
 - Warnings about pitfalls
 
 You MUST NOT:
+
 - Suggest Electron or Flutter
 - Suggest full rewrites
 - Ignore existing sidecar or station model
@@ -148,6 +161,7 @@ The WebView is a **control surface**, not a media engine.
 ## FIRST TASK WHEN STARTING
 
 Begin by:
+
 1. Identifying all HTML5 Audio usage
 2. Proposing the native audio engine design
 3. Defining the minimal command interface