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/.pi/extensions/gate/enrich.js

@@ -151,10 +151,32 @@ function enrichCteResultColumns(payload, planTables, getColumns) {
 	return { ...payload, columns };
 }
 
+// Contract C bis. Appends a deterministic "decisions of this phase" section built
+// from the session ledger, so the model's recap can stay thin (Discipline 6 exactness
+// comes from persisted state, not model prose). `decisions` is session-show's ledger
+// dump; `emits` is the phase's substantive decision-type list from workflow.yaml.
+// No matching decisions -> data returned unchanged. Pure: returns a NEW object.
+function appendLedgerSection(data, decisions, emits) {
+	const emitSet = new Set(emits || []);
+	const rows = (decisions || []).filter((d) => d && emitSet.has(d.type));
+	if (rows.length === 0) return data;
+	const section = {
+		title: "Decisioni registrate in questa fase (dal ledger)",
+		items: rows.map((d) => ({
+			label: `${d.type}: ${d.subject}`,
+			value: d.detail || "",
+			kind: "decision",
+			rationale: d.rationale || "",
+		})),
+	};
+	return { ...data, sections: [...(data.sections || []), section] };
+}
+
 module.exports = {
 	memoizeGetColumns,
 	enrichCtePlanV2,
 	buildCteResultV2,
 	enrichCteResultColumns,
 	enrichPhaseSummaryV2,
+	appendLedgerSection,
 };