chore(tooling): add make validate-content for schema validation

Python script validates campaign YAML files against JSON schemas in
content/_schema/. Maps files to schemas by directory context (npcs/
→ npc-profile.schema.json, etc.). Skips comment-only placeholder stubs.

Addresses Hoshe #2 review item.

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

Makefile

@@ -2,7 +2,7 @@ GODOT := $(shell command -v godot4 2>/dev/null || command -v godot 2>/dev/null)
 
 .PHONY: help setup build client server test lint ci ci-client ci-server clean \
        decisions-sync decisions-coverage decisions-active decisions-orphan \
-       db-backup db-install
+       db-backup db-install validate-content
 
 # --- Configuration ---
 
@@ -30,6 +30,7 @@ help:
 	@echo "  make decisions-coverage Decision-to-ticket coverage by domain"
 	@echo "  make decisions-active   List active decisions"
 	@echo "  make decisions-orphan   Decisions without implementing tickets"
+	@echo "  make validate-content  Validate content YAML against schemas"
 	@echo ""
 	@echo "  GODOT_VERSION=4.6 make setup   Override Godot version"
 
@@ -127,6 +128,11 @@ decisions-active:
 decisions-orphan:
 	@db/connectors/sqlite-query "SELECT id, title FROM decisions WHERE type='confirmed' AND status='active' AND id NOT IN (SELECT DISTINCT decision_ref FROM tickets WHERE decision_ref IS NOT NULL)"
 
+# --- Content Validation ---
+
+validate-content:
+	@tooling/validate-content
+
 # --- Clean ---
 
 clean: