workstation-v0 aggregate shortcut and dock polish signals

[mdheller]

Closes #145.

What changed:

• Extended check-workstation-polish.sh to aggregate shortcut-map and GNOME dock/extension helper signals.
• Updated workstation-polish-validation smoke workflow to syntax-check the additional helpers and assert representative shortcut_map.* and gnome_dock.* keys.

Validation evidence:

• bash -n profiles/linux-dev/workstation-v0/bin/check-workstation-polish.sh
• bash profiles/linux-dev/workstation-v0/bin/check-workstation-polish.sh
• workflow smoke asserts existing mac_polish.* and keyboard_policy.* keys plus new shortcut_map.* and gnome_dock.* keys

Known gaps:

• This only extends the aggregate helper.
• It does not update sourceos status or doctor.sh consumers beyond their existing aggregate-helper integration.

Non-goals preserved:

• No sourceos changes.
• No doctor.sh changes.
• No package manifest changes.
• No GNOME appearance/keybinding/extension mutation.