refactor: introduce cargo workspace + psysonic-core crate (M1/7)

First milestone of the workspace crate split. Sets up the workspace
skeleton and extracts shared logging + cross-crate port traits into a
new psysonic-core crate.

  src-tauri/Cargo.toml            now defines [workspace]; top package
                                  becomes the workspace root.
  crates/psysonic-core/           new lib crate, no Tauri-handler code:
    src/logging.rs                full logging facade (was src/logging.rs)
    src/ports.rs                  PlaybackQuery + AnalysisOrchestrator
                                  trait declarations (no impls yet)

The top crate re-exports `psysonic_core::logging` and the
`app_eprintln!` / `app_deprintln!` macros so every existing
`crate::logging::*` and `crate::app_eprintln!` callsite keeps working
unchanged.

Port traits intentionally take `tauri::AppHandle` — psysonic-core is a
workspace-internal crate, so depending on Tauri here is a feature, not
a leak. Implementers will register themselves as
`Arc<dyn PlaybackQuery>` / `Arc<dyn AnalysisOrchestrator>` Tauri State
in M2/M3.

Behaviour preserving. Cargo check + clippy --workspace clean.

src-tauri/Cargo.lock

@@ -3608,6 +3608,7 @@ dependencies = [
  "libc",
  "lofty",
  "md5",
+ "psysonic-core",
  "reqwest",
  "ringbuf",
  "rodio",
@@ -3637,6 +3638,15 @@ dependencies = [
  "zbus 5.15.0",
 ]
 
+[[package]]
+name = "psysonic-core"
+version = "1.46.0-dev"
+dependencies = [
+ "libc",
+ "serde",
+ "tauri",
+]
+
 [[package]]
 name = "pxfm"
 version = "0.1.29"

src-tauri/Cargo.toml

@@ -1,13 +1,22 @@
+[workspace]
+members = ["crates/*"]
+resolver = "2"
+
+[workspace.package]
+version = "1.46.0-dev"
+edition = "2021"
+rust-version = "1.89"
+
 [package]
 name = "psysonic"
-version = "1.46.0-dev"
+version.workspace = true
 description = "Psysonic Desktop Music Player"
 authors = []
 license = ""
 repository = ""
 default-run = "psysonic"
-edition = "2021"
-rust-version = "1.89"
+edition.workspace = true
+rust-version.workspace = true
 
 [lib]
 name = "psysonic_lib"
@@ -21,6 +30,7 @@ path = "src/main.rs"
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
+psysonic-core = { path = "crates/psysonic-core" }
 tauri = { version = "2", features = ["tray-icon", "image-png"] }
 tauri-plugin-single-instance = "2"
 tauri-plugin-shell = "2"

src-tauri/crates/psysonic-core/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "psysonic-core"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+publish = false
+
+[dependencies]
+tauri = { version = "2" }
+serde = { version = "1", features = ["derive"] }
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"

src-tauri/crates/psysonic-core/src/lib.rs

@@ -0,0 +1,8 @@
+//! `psysonic-core` — workspace-internal shared primitives.
+//!
+//! Hosts the runtime logging facade (with `app_eprintln!` / `app_deprintln!`
+//! macros) and the cross-crate port traits used to break dependency cycles
+//! between `psysonic-audio`, `psysonic-analysis`, and other domain crates.
+
+pub mod logging;
+pub mod ports;

src-tauri/crates/psysonic-core/src/logging.rs

@@ -1,3 +1,10 @@
+//! Runtime logging facade.
+//!
+//! Provides level-gated `eprintln!` macros (`app_eprintln!` / `app_deprintln!`)
+//! that also append to a bounded in-memory ring buffer and a CLI-readable
+//! per-runtime log file. Live mode toggling at runtime via
+//! `set_logging_mode_from_str("off"|"normal"|"debug")`.
+
 #[cfg(unix)]
 use libc;
 use std::collections::VecDeque;
@@ -98,7 +105,7 @@ pub fn export_logs_to_file(path: &str) -> Result<usize, String> {
     Ok(lines)
 }
 
-pub(crate) fn log_timestamp_local() -> String {
+pub fn log_timestamp_local() -> String {
     let now = ::std::time::SystemTime::now()
         .duration_since(::std::time::UNIX_EPOCH)
         .unwrap_or_default();

src-tauri/crates/psysonic-core/src/ports.rs

@@ -0,0 +1,49 @@
+//! Cross-crate port traits.
+//!
+//! These traits exist purely to break dependency cycles that would otherwise
+//! force `psysonic-audio` ↔ `psysonic-analysis` to depend on each other in
+//! both directions. Implementers register themselves as Tauri State on app
+//! bootstrap; consumers look them up via `app.try_state::<Arc<dyn _>>()`.
+//!
+//! Layout:
+//! - `AnalysisOrchestrator`  — implemented in `psysonic-analysis`, called from
+//!   `psysonic-audio` to enqueue full-buffer loudness/waveform analysis.
+//! - `PlaybackQuery`         — implemented in `psysonic-audio` on `AudioEngine`,
+//!   called from `psysonic-analysis` to ask "is this track currently playing?".
+
+use std::future::Future;
+use std::pin::Pin;
+
+use tauri::AppHandle;
+
+/// Read-only queries about the live playback session. Implemented on
+/// `AudioEngine` in `psysonic-audio`.
+///
+/// Registered as `Arc<dyn PlaybackQuery>` in Tauri State so non-audio crates
+/// can query without taking a hard dep on the audio crate.
+pub trait PlaybackQuery: Send + Sync + 'static {
+    /// `true` if `track_id` is the track currently being decoded/played.
+    fn is_track_currently_playing(&self, track_id: &str) -> bool;
+}
+
+/// Triggers full-buffer analysis on already-captured track bytes. Implemented
+/// on `AnalysisRuntime` in `psysonic-analysis`.
+///
+/// Registered as `Arc<dyn AnalysisOrchestrator>` in Tauri State so audio
+/// callsites (`stream::ranged_http`, `stream::track_stream`, `helpers`,
+/// `play_input`, `preload_commands`) can submit without depending on
+/// `psysonic-analysis`.
+pub trait AnalysisOrchestrator: Send + Sync + 'static {
+    /// Enqueue a CPU-seed analysis pass for `track_id` over the given byte
+    /// buffer. `high_priority` mirrors the HTTP-backfill head-insertion
+    /// behaviour for the currently playing track.
+    ///
+    /// Errors are stringified — audio callers only care about pass/fail.
+    fn submit_cpu_seed<'a>(
+        &'a self,
+        app: AppHandle,
+        track_id: String,
+        bytes: Vec<u8>,
+        high_priority: bool,
+    ) -> Pin<Box<dyn Future<Output = Result<(), String>> + Send + 'a>>;
+}

src-tauri/src/lib.rs

@@ -6,8 +6,10 @@ mod analysis_cache;
 mod analysis_runtime;
 pub mod cli;
 mod discord;
-pub(crate) mod logging;
 mod lib_commands;
+
+pub use psysonic_core::logging;
+pub use psysonic_core::{app_eprintln, app_deprintln};
 #[cfg(target_os = "windows")]
 mod taskbar_win;
 mod tray_runtime;