Tier 18.3: multi-leg Fabric Lakehouse Gold variant (4-dialect parity)

[jamezycesar-collab]

Summary

Adds ddl/multileg/05_multileg_gold_fabric_lakehouse.sql - the fourth-dialect variant of the multi-leg Gold layer. Brings multi-leg Gold to 4-dialect parity with the option Gold layout. Closes followup item #3 from the post-audit list.

Files changed

• ddl/multileg/05_multileg_gold_fabric_lakehouse.sql (NEW) - 4th-dialect mirror
• CHANGELOG.md - Tier 18.3 entry

What's in the new file

Object	Columns	Notes
gold.dim_multileg_strategy	9	SCD2 dimension of known strategies
gold.fact_multileg_option_events	75	Full post-Tier-17.5 column set incl. all CAT IM v4.1.0r15 §5.2 spec mapping columns
gold.fact_multileg_option_legs	15	Per-leg detail with canonical leg_*_indicator / leg_ratio_quantity names (Tier 17.3 renames)
gold.vw_multileg_option_lifecycle	view	Consolidated lifecycle view mirroring Delta + Hive variants

CHECK constraints

• fact_multileg_option_events.cat_event_code IN (25 multi-leg codes) - MLNO, MLOR, MLMR, MLCR, MLOA, MLIR, MLIM, MLIC, MLIMR, MLICR, MLCO, MLCOM, MLCOC, MLOM, MLOMR, MLOC, MLOCR, MLNQ, MLRQ, MLQS, MLQR, MLQC, MLQM, MLOS, MLOE
• fact_multileg_option_events.leg_count >= 2 (must be multi-leg)
• fact_multileg_option_legs.leg_side IN ('BUY', 'SELL')

Why

Pre-existing dialect-coverage gap. ddl/option/ had 4 dialects (Delta, Hive, Fabric Lakehouse, Fabric Warehouse) but ddl/multileg/ only had 3 - Fabric Lakehouse was missing. The gap predated the Tier 13 audit closure work and was flagged as followup item #3 in Tier 17.5's CHANGELOG.

Closing this aligns the multi-leg and option Gold layouts symmetrically. A Microsoft Fabric Lakehouse deployment can now provision both option and multi-leg facts from this repo without manual translation.

Coverage

All 8 guardrails:                  pass (exit 0)
DDL files in parity scope:        23 (was 22; +05_multileg_gold_fabric_lakehouse.sql)
Tables in 2+ dialects:            42 (unchanged)
New parity violations:             0
Allowlisted parity diffs:         12 (unchanged)
Allowlisted field mapping rows:    0 (unchanged - audit closed in Tier 17.5)

Open followups remaining

#	Item	Status
1	Validator regex hardening	✅ Tier 18.1
2	Empty allowlist housekeeping	✅ Tier 18.2
3	Multi-leg Fabric Lakehouse Gold variant	✅ this PR
4	Mapping CSV section/row polish (22 cosmetic refs)	open

Test plan

• All 8 guardrails pass (exit 0)
• 10/10 test__ddl_parser.py regression tests pass
• Column-name parity verified across all 4 dialects (no allowlist entries needed)
• Recurrence-safe precheck in push script