Add live syncback functionality and optimize service encoding

- Introduced a new endpoint `/api/syncback` for one-click full sync from Roblox Studio to the filesystem, eliminating the need for an active WebSocket connection.
- Implemented `SyncbackRequest` and `ServiceChunk` structures to handle service-level properties and child instances during syncback.
- Enhanced `encodeService` to include ObjectValue carriers for accurate reference handling and prevent data loss.
- Updated the syncback process to utilize Luau-style relative paths for reference attributes, improving path management and consistency.
- Integrated session caching in the matching algorithm to optimize performance during syncback operations.

These changes significantly improve the live syncback experience, ensuring reliable data synchronization and enhanced performance during development.

.cursor/rules/atlas-src.mdc

@@ -19,7 +19,7 @@ Pure functions: filesystem → instance tree → minimal patches → apply chang
 - `mod.rs` - System overview with detailed explanation
 - `patch_compute.rs` - Generate diffs (uses matching algorithm)
 - `patch_apply.rs` - Apply changes (resolves `Rojo_Ref_*` and `Rojo_Target_*` refs)
-- `matching.rs` - Forward sync matching algorithm (recursive change-count scoring)
+- `matching.rs` - Forward sync matching algorithm (recursive change-count scoring, `MatchingSession` caching)
 - `instance_snapshot.rs` - Core snapshot type
 
 ```rust
@@ -79,7 +79,7 @@ Instance names with forbidden filesystem chars (`<>:"/\|?*~`) are handled by:
 
 ### 3. Commands (`src/cli/`)
 
-- `serve.rs` - Live sync with WebSocket
+- `serve.rs` - Live sync with WebSocket; live syncback via `run_live_syncback()` + `build_dom_from_chunks()` (server restarts after syncback)
 - `build.rs` - Generate rbxl/rbxm/rbxmx/rbxlx
 - `upload.rs` - Upload to Roblox.com
 - `sourcemap.rs` - Generate sourcemaps
@@ -92,17 +92,19 @@ Reverse: Roblox file → filesystem
 
 - `snapshot.rs` - Convert instances to snapshots
 - `fs_snapshot.rs` - Filesystem representation
-- `matching.rs` - Syncback matching algorithm (recursive change-count scoring)
+- `matching.rs` - Syncback matching algorithm (recursive change-count scoring, `MatchingSession` caching)
 - `dedup_suffix.rs` - Dedup cleanup rules (gap-tolerant, base-name promotion, group-to-1)
 - `meta.rs` - Meta file read/write helpers (upsert/remove name, update ref paths)
-- `ref_properties.rs` - Ref property path linking (`Rojo_Ref_*`, tentative_fs_path)
+- `ref_properties.rs` - Ref property path linking (`Rojo_Ref_*`, tentative_fs_path, placeholder system)
 - `hash/` - Content hashing for change detection
-- `property_filter.rs` - Apply syncback rules
+- `fs_snapshot.rs` - Filesystem representation, parallel writes (`write_to_vfs_parallel`), ref path post-processing (`fix_ref_paths`)
+- `property_filter.rs` - Apply syncback rules (default: `sync_unscriptable = false`)
 
 ### 5. Web Server (`src/web/`)
 
-- `api.rs` - HTTP/WebSocket endpoints
-- `interface.rs` - Browser UI
+- `api.rs` - HTTP/WebSocket endpoints, including `POST /api/syncback` handler (`handle_api_syncback`)
+- `interface.rs` - Wire types: patches, `SyncbackRequest`, `ServiceChunk`, `SyncbackPayload`, `ServerExitReason`
+- `mod.rs` - `SyncbackSignal` (Mutex + Notify pattern), `LiveServer` (uses `tokio::select!` to wait for connections or syncback signal)
 - Protocol version enforcement
 
 ### 6. Project System (`src/project.rs`)
@@ -123,6 +125,8 @@ Parse/validate `.project.json5` (or legacy `.project.json`), handle nested proje
 
 **Key:** `src/serve_session.rs` manages active sessions
 
+**Live syncback integration:** The serve loop checks for `ServerExitReason::SyncbackRequested(payload)`. When received, calls `run_live_syncback()` which reconstructs the DOM from the plugin's rbxm blob + service chunks via `build_dom_from_chunks()`, runs `syncback_loop(incremental=false)` (clean mode), writes files via `write_to_vfs_parallel()`, refreshes git index, then restarts the serve loop.
+
 ### `rojo build`
 
 1. Load project
@@ -149,7 +153,7 @@ pub struct SyncbackRules {
     ignore_properties: IndexMap<Ustr, Vec<Ustr>>,  // Class → properties
     ignore_classes: Vec<String>,         // Classes to skip entirely
     sync_current_camera: Option<bool>,   // Default: false
-    sync_unscriptable: Option<bool>,     // Default: true
+    sync_unscriptable: Option<bool>,     // Default: false
     ignore_referents: Option<bool>,      // Skip Ref properties, default: false
 }
 ```
@@ -220,6 +224,7 @@ Review: `cargo insta review`
 **HTTP:**
 - `GET /` - Browser UI
 - `GET /api/rojo` - Server info (version, project name, protocol)
+- `POST /api/syncback` - Live syncback: full Roblox → filesystem sync (validates protocol, version, place ID)
 
 **WebSocket:** `ws://host:port/api/rojo`
 
@@ -312,6 +317,7 @@ to_writer(&mut buffer, &dom, dom.root())?;
 **Core:** rbx_binary, rbx_xml, rbx_dom_weak, memofs (local crate)
 **Async:** tokio, hyper, hyper-tungstenite
 **Serialization:** serde, json5, toml, yaml-rust2, csv
+**Float precision:** lexical-write-float (for roundtrip-safe f32/f64 formatting in JSON)
 **Utilities:** clap, anyhow, thiserror, crossbeam-channel, rayon, globset
 
 ## Module Organization
@@ -378,10 +384,11 @@ src/
     matching.rs         - Syncback matching algorithm
     dedup_suffix.rs     - Dedup cleanup rules
     meta.rs             - Meta file helpers
-  web/                  - HTTP/WebSocket
+  web/                  - HTTP/WebSocket (incl. SyncbackSignal, LiveServer)
+    interface.rs        - Wire types (patches, syncback requests)
   change_processor.rs   - Two-way sync filesystem writer
   git.rs                - Git integration (changed files, SHA1 hashing, auto-staging)
-  rojo_ref.rs           - Ref path system (Rojo_Ref_*, RefPathIndex)
+  rojo_ref.rs           - Ref path system (Rojo_Ref_*, RefPathIndex, Luau-style relative paths)
   variant_eq.rs         - Property value comparison
   lib.rs                - Public API
   main.rs               - CLI entry