Add subchunk_agg_check_rev8 with deterministic MC precompute and off-axis gain lookup

[nicklasorte]

Motivation

• Remove hot-path RNG reseeding and repeated per-azimuth antenna-pattern reconstruction to accelerate Monte Carlo aggregation while preserving deterministic behavior.
• Batch RNG draws and precompute azimuth-dependent antenna gains so the MC × azimuth hot path uses matrix math instead of repeated interpolation/rotation.
• Preserve function signature, output shape, NaN behavior and per-iteration seed identity for reproducibility.

Description

• Added a drop-in top-level optimized path subchunk_agg_check_rev8.m that keeps the same function signature as the existing subchunk_agg_check_rev7.m and preserves output shape and NaN handling.
• Deterministic RNG decoupling: precomputes rand_pr_all, rand_eirp_all, and rand_clutter_all in subchunk_agg_check_rev8.m using the original per-iteration seed identities (rand_seed1 + mc_iter, +1, +2) so each MC draw maps to the same identity as before.
• Azimuth vectorization: precomputes an off_axis_gain_matrix(num_bs, num_sim_azi) by computing relative azimuth rel_az = mod(bs_azimuth - sim_azimuth,360) once and performing nearest-neighbor lookup on a deduplicated antenna-pattern azimuth axis, eliminating repeated circshift/unique/nearestpoint operations in the MC hot path.
• RNG-free helper revisions: added helpers that accept precomputed random inputs and avoid internal rng calls: monte_carlo_Pr_dBm_rev2_app.m, monte_carlo_super_bs_eirp_dist_rev5.m, and monte_carlo_clutter_rev3_app.m.
• Chunked aggregation: performs MC computations in batch form and aggregates across azimuth in chunks (configurable chunk size azi_chunk) to avoid memory blow-up while removing the inner per-azimuth reconstruction loop.
• Validation helper: added validate_subchunk_agg_check_rev8_rev1.m to run side-by-side comparisons and timing between rev7 and rev8, checking size equality, NaN pattern equality, max/mean absolute differences, reproducibility, and percent speedup.
• Engineering constraints honored: no existing .m files were modified, the rev numbering pattern was followed (new helper names use incremented revisions), no parfor was introduced, and deterministic mapping to old seeds is preserved.

Testing

• Automated checks performed in this environment were limited to file-level verification and environment inspection, including printing the new files and checking for a MATLAB/Octave runtime; those checks succeeded at the file level.
• Runtime-based automated tests (numerical equivalence and timing) were not executed here because the environment lacks a MATLAB/Octave runtime (octave --version returned no binary).
• A validator script validate_subchunk_agg_check_rev8_rev1.m was included and will perform automated numerical equivalence, NaN-pattern, reproducibility, and runtime comparisons when run in a MATLAB/Octave environment.

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Codex Task