Feature/grs debug sampler

[sermengi]

Describe your changes

Summary

Introduces grs_debug_sampler.py, a reproducible scenario sub-sampler for smoke-testing the GRS pipeline, and post_sampling_analysis.ipynb, a companion notebook for inspecting the produced dataset.

grs_debug_sampler.py

A standalone CLI tool that draws a small (15–100), reproducible sample from the three GRS scenario pools (GPT, Gemini, Claude) and writes a JSONL output file plus a JSON manifest.

Sampling algorithm

• Phase 1 — one scenario drawn per obligation (alphabetical order, seed=42), guaranteeing full obligation coverage.
• Phase 2 — source-balanced fill on the remaining budget; shortfalls from exhausted sources are redistributed across non-exhausted ones.
• Final sample is shuffled with a second RNG (seed+1) for deterministic output ordering.

Schema normalisation
Adds normalize_record() to bridge the gap between the pipeline's native output schema (seed_trace, mutation_trace, governance_triggers) and the five sampler-required fields (source, obligation_id, scenario_type, mutation_type, primary_dimension). No pre-processing step needed.

Audit checks (recorded in manifest)

Check	Type	Rule
source_balance	Hard	Each source 33% ± 10%
obligation_coverage	Hard	All Phase-1 obligations in final sample
sample_size	Hard	15 ≤ n ≤ 100
id_uniqueness	Hard	No duplicate scenario_ids
dimension_coverage	Soft	All 5 dimensions represented

Usage

python3 grs_debug_sampler.py \
  --source-a datasets/grs_scenarios_v0.1/final/scenarios.jsonl \
  --source-b datasets/grs_scenarios_v0.2/final/scenarios.jsonl \
  --source-c datasets/grs_scenarios_v0.3/final/scenarios.jsonl \
  --target-n 50
Output defaults to datasets/debug/grs_debug_sample.jsonl and
datasets/debug/grs_debug_manifest.json.

###Test plan

• Run pytest test_grs_debug_sampler.py — all 15 tests pass
• Run sampler against the three scenario pools (--target-n 50) — overall
  audit PASS, manifest written, no drops
• Open post_sampling_analysis.ipynb and run all cells top-to-bottom —
  no errors, all sections render correctly

Write your issue number after "Fixes "

This PR does not intend to fix any specific issues.

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