Lock AZI_CHUNK default to 32 in rev13; add rev11↔rev13 validator and rev10↔rev13 benchmark

[nicklasorte]

Motivation

• Lock in the measured real-input chunk-size win with a minimal, auditable revision derived from rev11 so runtime improvements are preserved without broader refactors.
• Provide statistical validation and a compact real-input benchmark to ensure behavior is preserved and the speedup is measurable and repeatable.

Description

• Added subchunk_agg_check_maxazi_rev13.m which is a copy of rev11 with only the default AZI_CHUNK_DEFAULT changed to 32 and an inline comment noting the choice came from a real-input chunk sweep benchmark, while preserving RNG strategy, helper calls, off-axis logic, and overall structure.
• Added validate_subchunk_agg_check_maxazi_rev11_rev13_statistical.m which runs rev11 and rev13 on identical inputs, measures runtime, computes summary and tail statistics (mean, std, min, max, median, p90, p95, p99, and optional p99.9), prints a PASS/FAIL summary, returns a results struct, and fails-closed if configured thresholds (0.50 dB absolute or 5% relative) are exceeded.
• Added benchmark_subchunk_agg_check_maxazi_rev10_rev13_real.m which runs rev10 and rev13 on identical inputs, measures runtime_rev10 and runtime_rev13, reports speedup = runtime_rev10 / runtime_rev13, prints a concise summary, and returns a results struct.
• Intentionally did not modify rev10, rev11, or rev12, nor change RNG reseeding, helper-function behavior, or off-axis calculations.

Testing

• Performed repository-level checks to confirm the three new files exist and inspected their contents with automated file listing and text-display commands, and confirmed they implement the required interfaces and logic.
• Attempted to detect MATLAB/Octave runtime with octave --version, but the runtime was not available in the environment so no executions of the new MATLAB scripts were performed.
• No numeric runtime or statistical tests were executed in this environment; the validation and benchmark scripts are in place to be run in a proper MATLAB/Octave environment and will print/return the requested metrics when executed.

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Codex Task