refactor(src): dissolve basic.py, give every module an honest home

.felt/sp_validation/reserved-sasha/reserved-sasha.md

@@ -0,0 +1,11 @@
+---
+id: 01KVHAG0FSYA0Y6F5JDGTT6VNR
+name: 'Reserved: Sasha''s sp_validation work (don''t touch)'
+tags:
+    - sp-validation
+    - reserved
+    - guerrini
+created-at: 2026-06-20T03:32:01.913796095+02:00
+updated-at: 2026-06-20T03:32:01.913796095+02:00
+outcome: 'Hands-off zones owned by Sasha (Sacha Guerrini) on sp_validation: scratch/guerrini/ entirely, and the namaster_utils → source migration + Gaussian-sims de-duplication, which he reserved for HIS NEXT PR in the #197 review. Future workers/agents: do not refactor these; only mechanical import-path updates forced by a library change are OK (and should be flagged).'
+---

CLAUDE.md

@@ -38,15 +38,15 @@ is the container (full scientific stack pre-built). For a local dev environment:
 
 ### Core Package Structure (`src/sp_validation/`)
 - `b_modes.py`: Pure E-/B-mode decomposition (COSEBIS, pseudo-Cℓ)
-- `basic.py`: Basic utilities and mathematical functions
-- `calibration.py`: Shear calibration routines
+- `calibration.py`: Shear calibration — the `metacal` response class, galaxy selection masks (size/SNR), and m/c calibration routines
 - `cat.py`: Catalogue handling and manipulation
 - `cosmo_val.py`: Cosmology validation routines
 - `cosmology.py`: Cosmological calculations and theory
 - `galaxy.py`: Galaxy-specific processing
 - `io.py`: Input/output utilities
 - `plots.py`: Plotting functions
 - `rho_tau.py`: Rho and tau statistics calculations
+- `statistics.py`: Cosmology-independent statistics (jackknife resampling, χ²/PTE, covariance↔correlation, OneCovariance reshaping)
 - `survey.py`: Survey-level operations
 - `util.py`: General utilities
 

docs/source/post_processing.md

@@ -32,7 +32,7 @@ This step is carried out per patch. Parameters have to be set via the python con
 ### 2. Merge catalogues
 
 The patch-wise comprehensive catalogues extracted in the previous step are merged using the script `scripts/calibration/create_joint_comprehensive_cat.py`, which is a front-end
-of the `sp_validation` library class `run_joint_cat:JointCat`.
+of the `sp_validation` library class `catalog_builders:JointCat`.
 
 ### 3. Apply external masks