Add bounded orbit controls to the semantic wall view

[jonathanmcmichael]

Outcome

Allow a user to orbit around the semantic wall with a mouse drag while keeping the wall centered and the camera numerically stable.

Truth source

Use the current isometric view as the initial state. A full horizontal drag changes yaw; a full vertical drag changes pitch. Pitch must remain below the singular poles and all generated basis vectors must remain finite and normalized.

Invariants

• camera math is pure and unit tested separately from window events
• resize behavior and the semantic mesh mapping remain intact
• no Truck types enter renderer input
• interaction requests redraw only when camera state changes

Expected scope

Handle bounded mouse-button and cursor movement events in rustit-app, introduce a small camera state, and test normalization/clamping.

Non-goals

Pan, zoom, selection, touch gestures, inertia, persistence, and a general scene graph.

Acceptance and evidence

• dragging changes yaw and pitch in expected directions
• pitch clamps before camera-basis singularity
• repeated input never produces NaN or infinity
• release stops orbiting
• live Windows check plus cargo xtask verify pass

Dependencies: semantic renderer from #4. Coordinate with zoom issue #8 without combining the PRs.