context: Organized M1 Mirror documentation with parent-child README hierarchy

insight: DOCUMENTATION PATTERN: Studies use a two-level README hierarchy. Parent README at studies/{geometry_type}/README.md contains project-wide context (optical specs, design variables catalog, objectives catalog, campaign history, sub-studies index). Child README at studies/{geometry_type}/{study_name}/README.md references parent and contains study-specific details (active variables, algorithm config, results). This eliminates duplication, maintains single source of truth for specs, and makes sub-study docs concise. Pattern documented in OP_01_CREATE_STUDY.md and study-creation-core.md.

rule: When creating studies for a geometry type: (1) Create parent README with project context if first study, (2) Add reference banner to child README: '> See [../README.md](../README.md) for project overview', (3) Update parent's sub-studies index table when adding new sub-studies.


context: Created universal mirror optical specs extraction tool

insight: TOOL PATTERN: Mirror optical specs (focal length, f-number, diameter) can be auto-estimated from FEA mesh geometry by fitting z = a*r² + b to node coordinates. Focal length = 1/(4*|a|). Tool at tools/extract_mirror_optical_specs.py works with any mirror study - just point it at an OP2 file or study directory. Reports fit quality to indicate if explicit focal length should be used instead. Use: python tools/extract_mirror_optical_specs.py path/to/study

rule: For mirror optimization: (1) Run extract_mirror_optical_specs.py to estimate optical prescription from mesh, (2) Validate against design specs, (3) Document in parent README, (4) Use explicit focal_length in ZernikeOPDExtractor if fit quality is poor.


context: Implemented OPD-based Zernike method for lateral support optimization

insight: PHYSICS PATTERN: Standard Zernike WFE analysis uses Z-displacement at original (x,y) coordinates. This is INCORRECT for lateral support optimization where nodes shift in X,Y. The rigorous OPD method computes: surface_error = dz - delta_z_parabola where delta_z_parabola = -delta_r²/(4f) for concave mirrors. This accounts for the fact that laterally displaced nodes should be compared against parabola height at their NEW position. Implemented in extract_zernike_opd.py with ZernikeOPDExtractor class. Use extract_comparison() to see method difference. Threshold: >10µm lateral displacement = CRITICAL to use OPD.

rule: For mirror optimization with lateral supports or any case where X,Y displacement may be significant: (1) Use ZernikeOPDExtractor instead of ZernikeExtractor, (2) Run zernike_opd_comparison insight to check lateral displacement magnitude, (3) If max lateral >10µm, OPD method is CRITICAL.