feat(infospace): add L2 entity classification with type × VSM matrix (S2.9)

Implements the L2 typed-entities layer — each entity is assigned an
Entity Type (Element, Process, Relation, Principle, Institution) and a
VSM System (S1–S5) by an LLM, with one-sentence rationales for each.

New modules:
- markitect/infospace/classification.py — EntityClassification dataclass
  + ENTITY_TYPES / VSM_SYSTEMS controlled vocabularies
- markitect/infospace/classification_io.py — write/read classification
  files (YAML frontmatter + markdown body, mirrors evaluation_io)
- markitect/infospace/classifier.py — build_classification_prompt(),
  parse_classification_response(), run_entity_classification(); batch
  runner writes files incrementally (same resumable pattern as evaluate)

CLI: markitect infospace classify [--entity SLUG] [--provider P] [--model M]
  - Incremental skip: checks output/classifications/ for existing files
  - Defaults to openrouter provider; 2000 max_tokens (Gemini 2.5 Flash
    uses ~787 thinking tokens, so 800 was too low)

CLI: markitect infospace classify-summary [--update-metrics]
  - Entity type counts + VSM system counts with percentages
  - 5 × 6 type × VSM matrix (spots structural blind spots at a glance)
  - --update-metrics writes type_distribution, type_entropy,
    vsm_type_matrix_cells to metrics.yaml

Config: InfospaceConfig gains classifications_dir (default output/classifications)
Schema: schemas/typed-entity-schema-v1.0.md — type/VSM vocabulary tables,
  rationale format rules, validation rules, metrics enabled at L2
infospace.yaml: schemas.typed_entity references typed-entity-schema-v1.0.md

Seed classifications (3): division_of_labour (Process/S1),
  natural_price_as_central_price (Principle/S2),
  invisible_hand_mechanism (Principle/S4)

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

examples/infospace-with-history/output/classifications/division_of_labour.md

@@ -0,0 +1,30 @@
+---
+entity_slug: division_of_labour
+entity_type: Process
+vsm_system: S1
+type_rationale: The definition describes "the separation of a work process into distinct
+  tasks performed by specialised workers," which is an activity or transformation
+  in how work is conducted.
+vsm_rationale: Division of Labour directly concerns the organization and execution
+  of "productive activities" by specialized workers to increase output, which is the
+  core function of S1.
+classified_at: '2026-02-23T05:14:54.928218'
+---
+
+# Classification: Division Of Labour
+
+## Entity Type
+
+Process
+
+## VSM System
+
+S1
+
+## Type Rationale
+
+The definition describes "the separation of a work process into distinct tasks performed by specialised workers," which is an activity or transformation in how work is conducted.
+
+## VSM Rationale
+
+Division of Labour directly concerns the organization and execution of "productive activities" by specialized workers to increase output, which is the core function of S1.