pilotctl: honor hidden and renamed_to catalogue entries

[Alexgodoroja]

Problem

The signed catalogue marks io.pilot.smolmachines as "hidden": true, "renamed_to": "io.pilot.smol", but pilotctl read neither field:

• pilotctl appstore catalogue still listed "Smol Machines (renamed → io.pilot.smol)".
• pilotctl appstore install io.pilot.smolmachines failed with the misleading catalogue entry io.pilot.smolmachines has placeholder sha256 — the release pipeline hasn't filled this in yet.

Fix

• catalogueEntry gains Hidden and RenamedTo. Hidden entries are left out of the text listing; --json still returns them, with the flag.
• Install (with or without --version) follows renamed_to one hop and prints note: X was renamed to Y — installing Y on stderr. A rename pointing at a missing app gets a clear error instead.

Tests

zz_appstore_renamed_test.go covers the hidden listing, installing through a rename (unpacks the new app's bundle and prints the notice), and a rename to a missing app. go test ./cmd/pilotctl/ is green.

Found during the app-store audit.

🤖 Generated with Claude Code

[TeoSlayer]

Closing as superseded by #473, which merged today and implements hidden / renamed_to handling in the same files. The two conflict in appstore_catalogue.go and would declare the fields twice. One behaviour differs and is worth a follow-up if you want it: this PR follows a rename under --version and keeps hidden entries in --json; #473 refuses the pinned rename and omits hidden entries.