docs: add results/README.md — summary format, null result policy

results/README.md

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+# Results
+
+Tracked outputs from experiment runs. Large raw outputs are gitignored — only summaries are committed.
+
+## Structure
+
+```
+results/
+  summaries/    metric tables, key figures, per-phase result records (committed)
+  raw/          full embedding outputs, backtest CSVs (gitignored)
+```
+
+## Per-phase result record format
+
+Each concluded phase produces a result record in `summaries/`:
+
+```
+summaries/
+  phase-0-[pass|null].md
+  phase-1-[pass|null].md
+  ...
+```
+
+Each record must include:
+- Phase name and hypothesis
+- Key metrics (silhouette score, R², etc.) with confidence intervals where applicable
+- Baseline comparison
+- Verdict: PASS / NULL RESULT
+- If null: what was investigated, what was found, next step taken
+- Link to experiment git tag
+
+**Null results are valid research outputs and must be committed, not discarded.**