feat(opt): three efficiency levers for NL→SQL workflow

Lever 1: Join-graph via FK logics in annotations + suggest-fks command
  - TableAnnotation.foreign_keys field stores curated logical FKs (DWH has no FK constraints)
  - tht schema suggest-fks: mine from approved SQL, heuristics (time_key → dim_time),
    same-name discovery + explicit --assume flag for multi-owner PKs
  - mschema renders 【Foreign keys】 section populated; validation in merge.py
  - SKILL.md F4 now reads FKs from mschema-text, no custom data_time_key logic

Lever 2: Context-pack consolidation at kickoff (tht search pack)
  - Single embedding of question, reused for schema + evidence + solved searches
  - One command: tht search pack <question> --session <id> → retrieval_pack.md
  - Graceful degradation when Ollama/vector store unreachable (exit 0, empty sections)
  - SKILL.md F1 prescribes as first call; reduces model thinking turns via pre-retrieval

Lever 3: Phase-summary recap v2 auto-construction from session ledger
  - tht session show --json includes full decisions ledger
  - tht phase meta --json exports 'emits' (substantive decision types per phase)
  - Gate appends deterministic 【Decisioni registrate in questa fase】 section (appendLedgerSection)
  - Model authors only summary + checks; recap table comes from persisted state (exact by construction)
  - SKILL.md Disciplina 6: brief model output, gate fills the rest

Tests: 358 Python (including 10 FK + 3 pack + 1 session-ledger tests) + 111 JS gate tests, all pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

harness/tht/mschema/merge.py

@@ -12,4 +12,14 @@ def find_orphans(physical: PhysicalSchema, annotations: Annotations) -> list[str
         for column_name in table_ann.columns:
             if column_name not in table.columns:
                 orphans.append(f"{table_name}.{column_name}")
+        for fk in table_ann.foreign_keys:
+            label = f"{table_name}.fk({','.join(fk.columns)})->{fk.ref_table}"
+            ref = physical.tables.get(fk.ref_table)
+            if ref is None:
+                orphans.append(label)
+                continue
+            missing = [c for c in fk.columns if c not in table.columns]
+            missing += [c for c in fk.ref_columns if c not in ref.columns]
+            if missing:
+                orphans.append(label)
     return orphans