continue command should not pop an editor after resolution

[boneskull]

Running gh stack continue after conflict resolution opens an editor to edit the commit message. Let's skip that and accept the commit message as-is.

[boneskull]

@claude Can you look into solving this? It may just be adding a flag to RebaseContinue()

gh-stack/internal/git/git.go

Lines 289 to 292 in bdfb192

	func (g *Git) RebaseContinue() error {
	return g.runInteractive("rebase", "--continue")
	}

[boneskull]

Well, that didn't do anything.