[Bug]: First-Run Setup Progress Messages Don't Show Parallelism

[aayushch]

Description

Issue: First-Run Setup Progress Messages Don't Show Parallelism

Priority: Low (cosmetic only — no functional impact)
Component: ui/src-tauri/src/runtime.rs, ui/src-tauri/src/lib.rs

Problem

The first-run setup downloads Python, Node.js, and uv in parallel threads (via mpsc::channel in ensure_runtimes()), but the UI progress messages make it appear serial. The user sees:

"Downloading Python 3.12.13"
"Downloaded 5 MB / 28 MB"
"Downloaded 15 MB / 28 MB"
"Python 3.12.13 ready"
"Downloading Node.js 22.22.3"     ← appears to start only after Python finishes
"Downloaded 5 MB / 45 MB"
...

Similarly, steps 3 (deps) and 4 (n8n) run in parallel but the user may not notice since uv makes deps finish quickly.

Root Cause

RuntimeProgress::Bytes { downloaded, total } has no label identifying which download it belongs to. All three downloads' messages feed into a single "Preparing runtimes" step. When Python finishes before Node sends many messages (Python is ~28 MB vs Node ~45 MB), messages appear sequential.

The Bytes events can also cause the displayed download counter to jump backward (Python: 25 MB → Node: 5 MB) since each thread tracks its own downloaded counter independently.

Confirmed: Downloads ARE Parallel

The actual downloads run in separate std::thread::spawn threads and overlap on the network. Wall-clock time IS reduced. This is purely a UI visibility issue.

Proposed Fix

In ensure_runtimes(), wrap each thread's callback to convert Bytes into labeled Phase messages:

// In the python thread:
provision_python(&mut |p| {
    let labeled = match p {
        RuntimeProgress::Bytes { downloaded, total } => {
            let mb = downloaded / 1_048_576;
            RuntimeProgress::Phase(match total {
                Some(t) if t > 0 => format!("Python: {} / {} MB", mb, t / 1_048_576),
                _ => format!("Python: {} MB", mb),
            })
        }
        other => other,
    };
    let _ = tx.send(labeled);
});
// Same pattern for Node ("Node: X / Y MB") and uv ("uv: X / Y MB")

This makes interleaving visible without changing the RuntimeProgress enum or any other code. The user would see alternating "Python: 15 / 28 MB" and "Node: 10 / 45 MB" messages.

Files to Change

• ui/src-tauri/src/runtime.rs — wrap thread callbacks in ensure_runtimes()

Steps to Reproduce

1. Perform "first setup" run on Laya
2. The first-run setup downloads Python, Node.js, and uv in parallel threads (via mpsc::channel in ensure_runtimes()), but the UI progress messages make it appear serial. The user sees:

"Downloading Python 3.12.13"
"Downloaded 5 MB / 28 MB"
"Downloaded 15 MB / 28 MB"
"Python 3.12.13 ready"
"Downloading Node.js 22.22.3"     ← appears to start only after Python finishes
"Downloaded 5 MB / 45 MB"
...

Expected Behavior

The progress should be linear and not jump between parallel download statuses.

Actual Behavior

The first-run setup downloads Python, Node.js, and uv in parallel threads (via mpsc::channel in ensure_runtimes()), but the UI progress messages make it appear serial. The user sees:

Component

UI (Svelte frontend)

Laya Version

No response

Operating System

None

Logs / Screenshots

Additional Context

No response