refactor: resolve the project through selectors.ResolveProject

[NickJosevski]

Nine commands hand-rolled the same block: prompt for the project when it wasn't named, look it up when it was, error out in automation mode. It was copy-paste, not parallel evolution — the comment // project name is already provided, fetch the object because it's needed for further questions appeared verbatim 8 times.

They now call selectors.ResolveProject, which #609 adds next to the Project/FindProject primitives it composes.

release/{create,deploy,delete,list}, runbook/{list,run}, runbook/snapshot/list, channel/{create,list} — 9 files, -109 net lines.

Behaviour is unchanged

• Commands that echo Project <name> still do, on the same condition — the project came from the command line, so no prompt was shown.
• Automation-mode validation still runs before any API call. release delete in particular must reject a missing --version before looking the project up; its existing test asserts no project request is made, and caught me when I first got this wrong.

Not adopted: release-progression allow / prevent

These are the only two remaining selectors.Project callers. They have no lookup branch at all — when --project is supplied, selectedProject stays nil. Adopting the helper would change behaviour rather than just deduplicate, so they're left alone.

They're also independently broken. allow.go dereferences that nil:

if opts.Project.Value == "" {
    selectedProject, err = selectors.Project(...)   // only assigned when empty
}
opts.Project.Value = selectedProject.GetName()      // panics when --project was given

PromptMissing runs whenever !opts.NoPrompt, so octopus release-progression allow --project X panics interactively. prevent.go has the same missing branch and passes a nil project to SelectRelease. Confirmed (*projects.Project)(nil).GetName() panics. Worth its own fix + regression tests rather than being smuggled into a refactor.

Note on base

Based on nj/channel-list-view-delete (#609), which adds the helper. Retarget to main once that merges.