fix: stop task wait hanging on stdin and clearing the terminal line

[NickJosevski]

Fixes #526
Fixes #290

Two faults in task wait, both triggered by running it somewhere other than a plain interactive shell. They looked like separate reports; they are separate causes, in the same command.

#526 — hangs forever when shelled out to

task wait read stdin unconditionally to pick up piped task IDs:

taskIDs = append(taskIDs, util.ReadValuesFromPipe()...)

IsCalledFromPipe() is true whenever stdin is not a character device, and scanner.Scan() then blocks until the writer closes the pipe. A caller that shells out with stdin attached — Ruby's Open3.popen3, Python's subprocess.Popen — generally holds it open for the lifetime of the child, so the command never issued a single request, no matter that the task had long since finished.

This also explains the reporter's observation that runbook run worked fine from the same code: task wait is the only command in the CLI that calls ReadValuesFromPipe.

Fix: only consult stdin when no task IDs were given.

                        stdin held open by the caller
  before  octopus task wait ServerTasks-1 ...   STILL BLOCKED after 8s
  after   octopus task wait ServerTasks-1 ...   exited in 0s

Piping still works: echo ServerTasks-1 | octopus task wait behaves as before.

#290 — erases the terminal line when backgrounded

The spinner is installed in NewClientFactoryFromConfig:

if ask.IsInteractive() {
    httpClient = &http.Client{Transport: NewSpinnerRoundTripper()}
}

That runs from main.go:53, before cobra parses any flags. --no-prompt does not disable interactive mode until PersistentPreRunE (root.go:131), by which point the decision is already made — so --no-prompt never suppressed the spinner. Backgrounded, it redraws every poll by erasing the current terminal line, which is what made the terminal unusable.

Measured on a pty, counting ESC [ K (erase-line) sequences:

	erase-line sequences
--no-prompt, before	8
--no-prompt, after	0
no flag (interactive), after	7 — spinner still works

Setting CI=1 already worked, because that calls DisableInteractive() at main.go:48, early enough to be seen. That difference is what pinned the cause.

Fix: the round-tripper decides per request rather than at construction, once the flag has been applied.

Verification

Against a live instance, with a FIFO held open by a background writer to imitate popen3, timing the CLI process itself rather than the shell pipeline — the first attempt measured the pipeline and looked like no change at all.

Unit tests cover the resolution of task IDs versus stdin, and the spinner's per-request decision including the case where interactivity changes after the round-tripper is built, which is the actual bug.

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