Function projection

src/dashboard/memory_api.rs:357–363

`GET /api/plugins/holographic/projection` — 2D PCA of phase vectors, embedded as `[cos(p), sin(p)]` so wrapped phases compare correctly.

(
    State(state): State<DashboardState>,
    JsonQuery(params): JsonQuery<ProjectionParams>,
)

/// `GET /api/plugins/holographic/projection` — 2D PCA of phase vectors,
/// embedded as `[cos(p), sin(p)]` so wrapped phases compare correctly.
pub(crate) async fn projection(
    State(state): State<DashboardState>,
    JsonQuery(params): JsonQuery<ProjectionParams>,
) -> Json<Value> {
    let limit = coerce_limit(params.limit, 25, memory_service::projection_point_cap());
    Json(memory_service::projection_payload(&state, &params.q, limit).await)
}

/// `GET /api/plugins/holographic/similarity` — pairwise phase-cosine
/// similarity (`mean(cos(p_i − p_j))`) over all vectored facts.