Add progress and success output to remote install/update

[imattau]

Summary

• Remote install-ref / install <ref> / update previously printed nothing during the whole resolve-download-install pipeline, only a terse install order: ... line at the very end. On a slow relay or Blossom lookup (up to the existing network timeout) this looked hung, with no way to tell it was making progress or that anything actually happened.
• Adds stderr progress lines -- Connecting to N relay(s)... done in Xs, Resolving <publisher>/<name>..., Downloading <publisher>/<name> <version> (N mirror(s))... done in Xs (N bytes) -- matching the style npack search already uses, so stdout stays script-friendly.
• Adds a stdout installed <publisher>/<name> <version> line per package on success, matching the wording local .npk installs already use, in addition to the existing install order: ... summary.
• Verified live against a real relay (wss://relay.damus.io) with a nonexistent package -- connect/resolve progress prints correctly and the error is clear.

Test plan

• cargo fmt --check
• cargo clippy --all-targets
• cargo test (37 passed, no behavior change to covered paths)
• Manual smoke test against a real relay showing the new progress/error output
• docs/npack.1 regenerated via npack man (no diff)

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