test: assertions for validate_readme_structure (S2 Phase 1)

5 assertions: complete-README clean, missing-API detected, missing-list
contains 'API', community-tier skips enforcement.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

init.lua

@@ -127,6 +127,54 @@ end
         engine.test.assert(not string.find(asset_mermaid, "engine%.%*", 1, false), "generate_topology_block: asset-lib has no engine-node")
     end
 
+    -- ===== validate_readme_structure =====
+    do
+        local complete = [[
+# lib-core.foo
+Abstract.
+| Field | Value |
+|---|---|
+| Version | 0.1.0 |
+
+<!-- topology:start -->
+<!-- topology:end -->
+
+## API
+
+### `foo.bar()`
+Sig.
+
+## References
+- spec
+]]
+        local r = api.validate_readme_structure(complete, "core")
+        engine.test.equals(#r.missing_sections, 0, "validate: complete README -> no missing")
+        engine.test.assert(r.section_order_ok, "validate: complete README -> order ok")
+
+        local missing_api = [[
+# lib-core.foo
+Abstract.
+| F | V |
+
+<!-- topology:start -->
+<!-- topology:end -->
+
+## References
+- spec
+]]
+        local r2 = api.validate_readme_structure(missing_api, "core")
+        engine.test.assert(#r2.missing_sections > 0, "validate: missing API -> reports missing")
+        local has_api_missing = false
+        for _, s in ipairs(r2.missing_sections) do
+            if s == "API" then has_api_missing = true end
+        end
+        engine.test.assert(has_api_missing, "validate: missing-sections list contains 'API'")
+
+        -- Tier community: lockerer
+        local r3 = api.validate_readme_structure(missing_api, "community")
+        engine.test.equals(#r3.missing_sections, 0, "validate: tier=community -> no enforcement")
+    end
+
     engine.exit(engine.test.failures())
 end