[Bug]: [P3] Hybrid touch: held pan key suppresses drag-paint but a touch tap still places

Deferred from gds-code-review of spec-desktop-refusal-tooltip-shift-pan (2026-07-22, v1.84.0 via PR #590; originally minted 1.82.0 before main took that number).

With a hardware Shift (or Space) held on a touchscreen laptop and a paint tool armed, the press classifies as pan (classifyGesture pan key), but a release inside the 14px touch slop lands in onTap (src/game/engineWiring.ts), whose if (!touch) return guard only kills mouse taps, so placeSimpleBuild lays a paid strip. Mouse Shift+click is correctly dead; Space+touch-tap behaved this way before Shift joined, so this is pre-existing parity, not a regression.

Fix shape if picked up: thread the press's pan-key state into onTap (or latch it on the engine like downTouch) and skip placement when the key was held. Ship with a regression test covering both the suppressed tap and the normal touch tap. Review skill: /gds-code-review.

Start in src/game/engineWiring.ts by tracing classifyGesture's pan-key state into onTap, including the existing downTouch handling. Add regression coverage for suppressing a touch tap while Shift or Space is held, while preserving normal touch-tap placement; the issue is done when both cases pass.