Add Scorpion game variant

[austin-smith]

What Changed

• New Scorpion variant: single deck, Yukon-style group moves (any face-up card moves with everything on it), Spider-style same-suit building with automatically banked King-to-Ace runs, and a three-card stock dealt onto the first three piles at any time, once.
• Solver-backed hints via a Spider-modeled bounded best-first planner with a Scorpion-specific heuristic; the stock deal is hinted only when the search proves the tableau stuck.
• Full variant surface: rules/session/persistence/planner tests, probe ledger entry, docs/rules/scorpion.md, README rows, game-picker thumbnail, per-mode statistics, and a generated screenshot fixture.
• Spider's stock and completed-run pile views promoted to shared views (TableauStockView, CompletedRunPileView) used by both variants.
• Stock deals onto the tableau now animate (Scorpion and Spider): the session publishes each deal as an explicit event, and overlay cards fly from the stock to their piles, staggered and flipping mid-air. Undo flights flip mid-air on the way back (also fixing Klondike's face snap when drawn cards return to the stock), rapid deals and undo serialize instead of overlapping, and New Game/Redeal clear transient animation state the way game switches always have.

Why

Closes #50. Scorpion fills the gap between Yukon and Spider in the lineup; deals previously popped into place with no animation, which made the three-card stock deal illegible.

Validation

• Full test suite passes on macOS; iOS Simulator build clean.
• tools/hint-probe/run.sh scorpion 500: 14.8% hint-following win rate vs 2.8% random control, zero stalemate loops, zero revisit events, reproduced byte-identically across runs; run.sh all 500 reproduces every existing variant's ledger figure exactly.
• Simulator passes verified on video with frame extraction: deal shape, group drags, same-suit landings, kings-only empty columns, stock deal (including onto empty piles), auto-banking with reveal scoring, single-tap undo of a deal, hint flow including the stock-tap fallback, deal/undo flights (including rapid double-deal, undo mid-flight, and relaunch into a saved dealt game showing no replay), statistics, and the rules sheet.

UI Changes

• Scorpion board: three-card stock top-left, four completion piles over the right columns, seven-pile tableau.
• Game picker gains the Scorpion entry with a mini board silhouette.
• Deal flights for Scorpion and Spider; mid-air flips on deal and undo flights.

[austin-smith]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Chef's kiss.

Reviewed commit: 42e1f59fcb

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