Seed native coefficient/root touch prototype

[isomorphisms]

What this seeds

• native Android NativeActivity + EGL/GLES shell based on the touch/render loop already proven in Wegert
• split complex-plane view: numbered coefficient handles on the left, unnumbered root dots on the right
• runtime-degree monic polynomials zⁿ + cₙ₋₁zⁿ⁻¹ + … + c₁z + c₀, with degrees 1–12 in the current mobile renderer
• − / + degree controls: increasing degree multiplies by z and adds a zero root; decreasing degree removes the root nearest the origin
• immediate coefficient → root and root → coefficient updates while dragging
• generic simultaneous coefficient → root solving, seeded from the previous frame with a bounded-circle fallback
• minimum-total-motion root assignment so the unnumbered root dots avoid gratuitous swaps
• repeated-root multiplicity shown as concentric circles
• host-side polynomial checks for quadratic, cubic, sextic, degree 12, repeated roots, and root continuity
• Android CI build plus emulator smoke tests for both drag directions, repeated-root rendering, and raising the polynomial to degree 3 and dragging c₂

The initial state remains the original monic quadratic. The degree-12 ceiling is an implementation bound for the current touch/rendering slice, not a return to a quadratic-only model.