Complete or document Sampling Design State detection (only handles SDS 1-2)

[cnicholas]

The docstring for __calculate_sampling_design_state() (lines 1385-1399) describes 6 sampling design states but the implementation only handles SDS 1 and 2.

From docstring

- SDS1: every (k,t) cell has n>=2
- SDS2: every (k,t) cell has n==1
- SDS3: mixture of replication (some n==1 and some n>=2) and/or missing (k,t) cells
- SDS4: single design condition over time (K==1 with time present)
- SDS5: nested design (>=2 design vars) with asynchronous time coverage
- SDS6: unstructured fallback (no time OR cannot form (k,t) cells)

Actual implementation

if all(group_sizes>=2): out = 1
if all(group_sizes==1): out = 2
# Everything else returns 0

Impact

• Misleading documentation
• Silent failures for SDS 3-6 cases
• Incomplete feature

Fix Options

Option 1: Implement SDS 3-6 detection
Option 2: Update docs to state only SDS 1-2 supported and raise error for other cases

Files

• analysis_dataset.py