feat(l2): make monitor quit

[gianbelinche]

Motivation
When the monitor is quitted with Shift + Q it closes the monitor but does not end the process

Description
Changed the L2 task initialization to use JoinSet instead of a TaskTracker, so it can be joined and end the process if it ended.

How to test

• Add --monitor to the init-l2-no-metrics target in crates/l2/Makefile.
• Run a Sequencer (I suggest make restart in crates/l2).
• Run the prover with make init-prover in crates/l2.
• Run make test in crates/l2.
• Press Shift + Q to close the monitor

Closes #3512

[Copilot]

Pull Request Overview

This PR switches the L2 monitor shutdown handling from using TaskTracker to JoinSet so that quitting the monitor (Shift + Q) ends the process cleanly.

• Break out of the sequencer loop when the first L2 task completes successfully.
• Replace top‐level TaskTracker in the CLI command with a JoinSet and add a select branch to handle monitor quit.
• Persist node config and cancel tasks when the monitor is closed.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
crates/l2/sequencer/mod.rs	Changed the Ok(Ok(_)) match arm to break out of the join loop.
cmd/ethrex/l2/command.rs	Imported JoinSet, initialized it, replaced tracker.spawn with join_set.spawn, and added a new select branch on join_next().

Comments suppressed due to low confidence (1)

cmd/ethrex/l2/command.rs:231

• There are no tests verifying that pressing Shift+Q triggers this branch, cancels tasks, and persists the node config. Consider adding an integration test for the monitor shutdown flow.

                    _ = join_set.join_next() => {

[Copilot]

When handling the first completed child task via join_set.join_next(), you don’t abort or await the remaining tasks. Explicitly abort pending tasks or await their completion to avoid background leaks.

[github-actions]

Lines of code report

Total lines added: 6
Total lines removed: 0
Total lines changed: 6

Detailed view

+-----------------------------------+-------+------+
| File                              | Lines | Diff |
+-----------------------------------+-------+------+
| ethrex/cmd/ethrex/l2/command.rs   | 461   | +5   |
+-----------------------------------+-------+------+
| ethrex/crates/l2/sequencer/mod.rs | 173   | +1   |
+-----------------------------------+-------+------+

[tomip01]

LGTM, just one small comment