fdctl: add monitor --topo flag

[ripatel-fd]

Allows running monitor for custom topologies

[Copilot]

Pull request overview

Adds support for selecting an alternate predefined topology when running fdctl monitor, enabling the monitor UI to attach to non-default topologies.

Changes:

• Extend monitor command args with a topo string buffer to store the selected topology name.
• Parse a new --topo flag in monitor and reconstruct config->topo by looking up the named action in ACTIONS[].
• Invoke topology reconstruction at the start of monitor_cmd_fn.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/app/shared/fd_action.h	Adds monitor.topo storage to args_t so the selected topology name can be passed through execution.
src/app/shared/commands/monitor/monitor.c	Parses --topo, looks up the matching action topology via ACTIONS[], and rebuilds config->topo before starting the monitor.

[Copilot]

The length check for --topo reports "Unknown --topo", but the actual failure mode here is that the provided string is too long for args->monitor.topo. This is misleading for users and also logs the full (potentially very large) input string. Consider changing the message to something like "--topo too long (max N)" and/or truncating the logged value to the buffer size.

Suggested change

	if( FD_UNLIKELY( topo_name_len > sizeof(args->monitor.topo)-1 ) ) FD_LOG_ERR(( "Unknown --topo %s", topo_name ));
	ulong max_topo_len = sizeof(args->monitor.topo) - 1UL;
	if( FD_UNLIKELY( topo_name_len > max_topo_len ) )
	FD_LOG_ERR(( "--topo too long (max %lu chars)", max_topo_len ));