Closes#57. Adds three OnInputAction switch cases (SelectLeft,
SelectDblLeft, UseSelected) and three private helpers
(PickAndStoreSelection, UseCurrentSelection, SendUse). Single-click
selects but does not Use; double-click selects + Uses; R hotkey
sends Use on the existing _selectedGuid. ImGui mouse-capture
filtering already happens in InputDispatcher — no new guard needed.
Diagnostic lines emitted for log grep:
[B.4b] pick guid=0x{guid:X8} name={label}
[B.4b] use guid=0x{guid:X8} seq={seq}
Also adds a one-line doc comment on _selectedGuid clarifying its
dual-purpose role (combat Q-cycle + interaction click), per the Task 3
review.
Build green; tests 1046/1054 (8 pre-existing-baseline fails
unchanged). Switch-case behavior verified at runtime via the Holtburg
inn doorway visual test (per spec §Testing → Runtime verification).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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