Add single IPO analyst report generator

Request:
- Let the analyst skill generate a Markdown report directly when a new IPO ticker is provided.

Changes:
- Add scripts/generate_ipo_report.py for stage-safe single-ticker reports from the v0 analysis dataset.
- Auto-select T1 reports when structured allotment demand exists and otherwise use T0 prospectus-stage reporting.
- Keep post-listing D1/D5/D20/D60 outcomes out of prediction reports while using historical buckets for calibration.
- Document the workflow in the analyst skill and README.

Verification:
- Ran py_compile for scripts/generate_ipo_report.py.
- Generated stdout dry-run reports for 06106 and 06658.
- Wrote temporary Markdown reports under /tmp for output-path validation.
- Ran git diff --check.

Next useful context:
- Before generating a report for a ticker absent from the analysis dataset, run archivist updates and rebuild scripts/build_analysis_dataset.py.

README.md

@@ -155,6 +155,19 @@ The v0 model is documented in `rules/ipo_score_v0.yaml`. It writes `data/snapsho
 
 The model separates T0 prospectus inputs from T1 allotment inputs. D1/D5/D20/D60 returns are labels for calibration and review, not prediction inputs.
 
+## Single IPO Markdown Report
+
+Use the analyst report generator after the archive and model dataset are current:
+
+```bash
+.venv/bin/python scripts/build_analysis_dataset.py --as-of 2026-06-15T15:00:00Z
+.venv/bin/python scripts/generate_ipo_report.py 06106 --stage auto
+```
+
+The generator writes `reports/{date}_{ticker}_{stage}_analysis.md` by default. It auto-selects `T1_allotment` when structured allotment-demand facts exist; otherwise it generates a `T0_prospectus` report. Use `--stdout` for a dry run or `--output` to choose a specific Markdown path.
+
+Prediction reports are stage-safe: T0 reports use only prospectus-stage facts and T0 calibration, while T1 reports add allotment demand and T1 calibration. Post-listing D1/D5/D20/D60 performance stays out of prediction reports and is reserved for review cards.
+
 ## Incremental Archive Sync
 
 The archivist keeps a per-ticker sync ledger so repeated updates can focus on missing stages: