feat(example): add supply-chain-vsm composition demo (S3.5)

Demonstrates infospace composition: the Wealth of Nations infospace is
used as a discipline, applying Smith's economic framework as a lens to
analyse modern supply chain management concepts.

New example: examples/supply-chain-vsm/
- infospace.yaml binding WoN as discipline (../infospace-with-history)
- 3 source documents: coordination mechanisms, capital & inventory,
  market structure (~400 words each, original content)
- supply-chain-entity-schema-v1.0.md with WoN Concept required section
- won-mapping-schema-v1.0.md with Conceptual Continuity rating
- artifacts/won-reference/core-entities.md — 12 curated WoN entities
  for injection as discipline context
- 8 hand-crafted entity files demonstrating LLM output format
- 3 mapping files with full rationale and VSM inheritance chains
- Viable: YES (5/5 thresholds)

Key mappings demonstrated:
  Demand Signal          → Effectual Demand        (Strong, S2)
  Vendor-Managed Inventory → Division of Labour    (Strong, S1/S2)
  Just-in-Time Inventory → Circulating Capital     (Strong, S1/S3)
  Bullwhip Effect        → Natural Price           (Moderate, S2)
  Platform Intermediary  → Merchant Capital        (Strong, S2/S4)
  Monopsony Power        → Combination of Masters  (Strong, S3*)

Platform fix: entity_parser.py now recognises ## Supply Chain Domain
as a domain alias for ## Economic Domain, enabling composed infospaces
to use their own domain section name.

Tutorial §13 rewritten with real commands, real output, and the full
mapping table from the demo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/supply-chain-vsm/artifacts/sources/market-structure.md

@@ -0,0 +1,71 @@
+# Market Structure in Modern Supply Chains
+
+## Platform Intermediaries
+
+A platform intermediary in a supply chain context is a company that does
+not itself produce or consume goods but instead controls the infrastructure
+through which buyers and sellers transact. Platform intermediaries include
+e-commerce marketplaces (Amazon, Alibaba), logistics platforms (Flexport,
+FreightOS), and procurement networks (Coupa, Ariba). Their value lies not
+in physical capital but in network effects: the platform becomes more
+valuable to each participant as the total number of participants grows.
+
+Platform intermediaries extract value by charging transaction fees, selling
+data analytics, providing financing, or leveraging their position to capture
+margin that previously accrued to producers or carriers. Their market power
+derives from control of the matching infrastructure: a seller who abandons
+the platform loses access to the buyer network; a buyer who abandons the
+platform loses access to the supplier network.
+
+Unlike traditional merchant intermediaries — who bought and sold goods,
+bearing inventory risk — platform intermediaries transfer inventory risk to
+the counterparties. The platform earns commission on each transaction but
+holds no stock; the asymmetry concentrates profit in the intermediary while
+concentrating risk in producers and carriers.
+
+## Monopsony and Buyer Power
+
+Monopsony is market power on the buyer's side: a situation in which a
+single buyer (or a small number of buyers acting in concert) faces many
+sellers. In supply chains, monopsony manifests when a large retailer or
+manufacturer is the dominant customer for a category of suppliers. The
+buyer's ability to credibly threaten to switch suppliers — or to reduce
+purchase volumes — gives it negotiating leverage that suppliers cannot
+easily counter.
+
+Buyer power is exercised through price pressure (demanding lower unit costs
+in each contract renegotiation), terms pressure (extending payment terms,
+imposing fines for delivery failures), and specification creep (adding
+requirements without cost compensation). Suppliers facing strong buyer power
+are systematically squeezed: their margins decline, their ability to invest
+in quality and capacity is constrained, and their bargaining position
+deteriorates further as the buyer grows.
+
+The long-run consequence of sustained monopsony pressure is supplier
+consolidation — weaker suppliers exit, leaving the buyer with fewer but
+larger suppliers — and supply fragility, as the surviving suppliers have
+insufficient margin to hold safety stock or invest in resilience.
+
+## Market Concentration and Single-Source Dependencies
+
+Single-source dependency occurs when a supply chain relies on one supplier
+for a critical component or material with no readily substitutable
+alternative. Single-source situations arise from supplier specialisation
+(only one firm has the required capability), geographic concentration (all
+competent suppliers are in one region), or deliberate buyer policy (choosing
+the best supplier and extracting maximum scale economies).
+
+Single-source dependencies concentrate supply chain risk. When a
+single-sourced supplier fails — due to fire, flood, earthquake, insolvency,
+or geopolitical disruption — the buyer has no immediate alternative. The
+semiconductor industry exemplifies this: certain advanced logic chips can
+only be produced by one or two foundries globally, making entire sectors
+of the world economy dependent on the operational continuity of a small
+number of facilities in Taiwan and South Korea.
+
+From a market structure perspective, single-source suppliers possess
+temporary monopoly power: during a supply disruption, they can charge
+prices far above their normal level, because no substitute exists. Smith's
+analysis of monopoly price — that it is the highest that can be squeezed
+from buyers — applies directly: a disrupted single-source supplier in a
+critical category faces demand that is inelastic in the short run.