feat(infospace): add collection-level quality checks C1–C5 (S2.4)

Five concern checks: Redundancy (embedding/word overlap), Coverage
(FCA gap analysis), Coherence (graph connectivity), Consistency
(cycle detection), Granularity (Shannon entropy). Orchestrator runs
all or selected checks, CLI `markitect infospace check` command added.

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

markitect/infospace/cli.py

@@ -273,3 +273,61 @@ def viability(config_path: Optional[str]):
         click.echo(f"Viable: YES ({state.viability_pass_count}/{state.viability_total_count} thresholds met)")
     else:
         click.echo(f"Viable: NO ({state.viability_pass_count}/{state.viability_total_count} thresholds met)")
+
+
+# ── check ───────────────────────────────────────────────────────────
+
+
+@infospace_commands.command()
+@click.option("--config", "config_path", default=None, help="Path to infospace.yaml.")
+@click.option(
+    "--concern", "concerns", multiple=True,
+    type=click.Choice(["redundancy", "coverage", "coherence", "consistency", "granularity"]),
+    help="Run specific concern(s). Omit to run all five.",
+)
+@click.option("--json", "as_json", is_flag=True, help="Output results as JSON.")
+def check(config_path: Optional[str], concerns: tuple, as_json: bool):
+    """Run collection-level quality checks (C1–C5)."""
+    cfg, cfg_path = _load_config_or_exit(config_path)
+    root = cfg_path.parent
+
+    entities_dir = root / cfg.entities_dir
+    if not entities_dir.is_dir():
+        click.echo("Error: No entities directory found.", err=True)
+        raise SystemExit(1)
+
+    entity_list = parse_entity_directory(entities_dir)
+    if not entity_list:
+        click.echo("No entities to check.")
+        return
+
+    from markitect.infospace.checks import run_all_checks
+
+    checks_list = list(concerns) if concerns else None
+
+    report = run_all_checks(
+        entities=entity_list,
+        checks=checks_list,
+    )
+
+    if as_json:
+        import json
+        click.echo(json.dumps(report.to_dict(), indent=2))
+    else:
+        click.echo(f"Collection checks — {len(entity_list)} entities\n")
+        d = report.to_dict()
+        for concern_name, concern_data in d.items():
+            label = concern_data.get("concern", concern_name.upper())
+            click.echo(f"  {label} — {concern_name}")
+            for k, v in concern_data.items():
+                if k == "concern":
+                    continue
+                click.echo(f"    {k}: {v}")
+            click.echo()
+
+    # Show summary metrics
+    m = report.metrics()
+    if m and not as_json:
+        click.echo("Metrics summary:")
+        for k, v in sorted(m.items()):
+            click.echo(f"  {k}: {v:.4f}")