fix: opening a different graph in a diagram that is already open

[endrix]

The problem

The open command stashes the requested graph name, then calls vscode.openWith:

if (requestedNetwork) {
    putPending(state.pendingNetworkBySourceUri, sourceUri.toString(), requestedNetwork);
}
await vscode.commands.executeCommand('vscode.openWith', sourceUri, profile.customEditorViewType);

The stash is read by the initial model request. An editor that already exists does not make one — openWith focuses it instead. So asking for a different graph inside a file you were already looking at did nothing at all: the name was recorded, the tab came forward, and the diagram kept showing what it showed before.

Moving between the graphs in one file is the ordinary use of this command, and it is the case where doing nothing is hardest to read, because the command plainly did something: the editor took focus. There is no way for a reader to tell a command that silently declined from one that was never wired up.

The change

When a diagram for the file is already open, refresh it with the requested name.

A refresh already carries networkName into a fresh model request — that is the mechanism a drill-down relies on — so this reuses it rather than adding a second path. Whether the diagram is already open is asked before opening, since opening is what makes it true.

The split-view command had the same shape and is fixed the same way. Leaving a known identical bug beside a fixed one is worse than fixing both.

Neither path changes for a diagram that is not yet open: the stash is still what the initial request reads, and no extra round trip is added to a fresh open.

Verified

npm run build, npm run typecheck (5/5), npm run check:neutrality (5/5), npm test — green by exit code.