Show commander tax in perpetual mana cost overlay

[MostCromulent]

Summary

• Commander tax isn't technically a perpetual effect, but the perpetual overlay was added to answer "what does this card actually cost?" — commander tax is the most common reason a commander's cost differs from its printed cost, so it fits naturally here and a separate overlay setting isn't justified
• When the "perpetual mana cost" overlay is enabled, commanders in the command zone now display their mana cost including accumulated commander tax ({2} per previous cast from command zone)
• The tax is layered dynamically on top of any existing perpetual cost adjustments in the getter, keeping the perpetual calculation pipeline unchanged

Design notes

Scope: The overlay shows permanent/intrinsic modifiers only (perpetual effects + commander tax), not external battlefield-state cost modifiers like Foundry Inspector. Similarly, cards that specifically offset commander tax — like Myth Unbound ({1} less per cast) or Liesa, Shroud of Dusk (pay life instead of tax) — are not reflected in the overlay. This is an existing limitation of the perpetual overlay — it has never accounted for external modifiers — and commander tax doesn't change that.

View update trigger: The mana cost overlay reads from a cached trackable property, so it needs an explicit updateManaCostForView() call to refresh. Three locations were considered:

• Player.incCommanderCast() — card is on the stack when this fires, so the zone-gated getter returns base cost (no effect)
• GameAction.changeZone() — multiple branches need the trigger, and setPerpetual() fires before the zone is set
• Card.setZone() — fires after zone assignment, single point for all transitions, gated behind isCommander(), consistent with the 50+ existing view.update*() calls in Card.java

Card.setZone() was chosen for simplicity and completeness.

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