docs(air-painting): silence ORT partial-EP warning at session creation

What

Sets logSeverityLevel: 3 (errors only) on both ONNX Runtime sessions created by the air-painting example, matching what depth-estimation already does via sessionOptions. Regenerated apps/docs/lib/examples-source.generated.ts.

Why

Enabling the camera on /examples/air-painting in next dev pops a Console Error overlay on every session creation:

[W:onnxruntime:, session_state.cc:1367 VerifyEachNodeIsAssignedToAnEp] Some nodes were not assigned to the preferred execution providers which may or may not have an negative impact on performance. e.g. ORT explicitly assigns shape related ops to CPU to improve perf.
    at async createSession  examples/air-painting/ort-webgpu.ts (57:12)
    at async createSiblingSession  examples/air-painting/ort-webgpu.ts (126:19)
    at async initialize  examples/air-painting/ort-runtime.ts (291:16)
    at async Object.enableCamera  examples/air-painting/renderer.ts (42:11)

The message is informational (ORT pins shape ops to CPU by design), but the wasm build writes WARNING-level logs to stderr, Emscripten forwards stderr to console.error, and the Next dev overlay treats that as an error.

Checks

• pnpm exec vitest run apps/docs/examples/air-painting: 8 files, 79 tests pass.
• logSeverityLevel is a typed InferenceSession.SessionOptions field in onnxruntime-common 1.27.0.
• Docs-only change under apps/docs/**, no changeset per CONTRIBUTING.