feat(installation-manager): render install/download progress bar

Real Composer shows a ProgressBar during InstallationManager's
waitOnPromises (`Package operations: N installs` ... `0/109 [>---] 0%`
... `100%`), but this port never wired one up: output_progress was set
by callers and never consulted. This adds the same gating PHP uses
(output_progress, ConsoleIO, not CI, not debug, more than one
operation) for both the download phase and the install/extract phase.

The port runs downloads/installs serially rather than as concurrently
polled promises (see the existing TODO(phase-c-promise) notes), so
there is no active-job count to poll for intermediate snapshots.
Stepping the bar per completed operation was tried first, but it
interleaves with the "- Installing ..." lines mid-terminal-line since
both share the same overwrite/newline state; rendering a single 0% ->
100% jump after each phase avoids that garbling at the cost of the
timing-driven intermediate snapshots real Composer shows.

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