feat(api-discovery): add tier=module for module-repo lints

Modules differ from libs structurally: they have no consumable public
API (their hooks like M.update are engine-contract, documented in the
engine spec, not in the module). The README convention for modules
replaces the ## API section with ## Controls + ## Demonstrates.

This adds tier=module validation in validate_readme_structure with
MUST-sections H1, Abstract via Module-ID badge, Topology + Topology-
Block markers, Controls, Demonstrates, References. Order-check
ensures Demonstrates precedes References (no API exists to check).

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

init.lua

@@ -144,6 +144,10 @@ end
 -- Tier "core" enforces: H1, Abstract, Badges, Topology, Topology-Block, API, References.
 -- Tier "engine" enforces the same MUST-sections, but the Badges check accepts
 --   any bold key:value line (engine README has no Lib-ID; instead Version/License).
+-- Tier "module" enforces: H1, Abstract via Module-ID badge, Topology + Topology-Block,
+--   Controls, Demonstrates, References. Modules have no consumable public API
+--   (engine-hooks are documented in the engine spec), so ## API is replaced by
+--   ## Controls + ## Demonstrates.
 -- Tier "community" enforces nothing (returns empty result).
 -- Returns: { missing_sections = [...], section_order_ok = bool }
 function M.validate_readme_structure(markdown_string, tier)
@@ -151,22 +155,38 @@ function M.validate_readme_structure(markdown_string, tier)
         return { missing_sections = {}, section_order_ok = true }
     end
 
-    -- Both "core" and "engine" tiers use the same MUST-sections list.
-    -- Difference is handled upstream (engine tier skips parse_lua_surface etc.).
     local missing = {}
-    local checks = {
+    local checks
-        { name = "H1",             pattern = "^#%s+%S" },
-        { name = "Badges",         pattern = "\n%*%*Lib%-ID:%*%*%s*lib%-" },
-        { name = "Topology",       pattern = "\n##%s+Topology[%s\n]" },
-        { name = "Topology-Block", pattern = "<!%-%-%s*topology:start" },
-        { name = "API",            pattern = "\n##%s+API[%s\n]" },
-        { name = "References",     pattern = "\n##%s+References[%s\n]" },
-    }
 
-    -- Engine-tier: relax the Badges check (engine uses "Version", "License" etc.
+    if tier == "module" then
-    -- instead of a "Lib-ID:" prefix — engine is not a lib).
+        -- Module-tier: no ## API (engine-hooks aren't a consumable surface);
-    if tier == "engine" then
+        -- Badges identifies the module via **Module-ID:**; Controls + Demonstrates
-        checks[2] = { name = "Badges", pattern = "\n%*%*[%w%-]+:%*%*" }
+        -- are the module-specific README sections.
+        checks = {
+            { name = "H1",             pattern = "^#%s+%S" },
+            { name = "Badges",         pattern = "\n%*%*Module%-ID:%*%*%s*" },
+            { name = "Topology",       pattern = "\n##%s+Topology[%s\n]" },
+            { name = "Topology-Block", pattern = "<!%-%-%s*topology:start" },
+            { name = "Controls",       pattern = "\n##%s+Controls[%s\n]" },
+            { name = "Demonstrates",   pattern = "\n##%s+Demonstrates[%s\n]" },
+            { name = "References",     pattern = "\n##%s+References[%s\n]" },
+        }
+    else
+        -- Both "core" and "engine" tiers use the same MUST-sections list.
+        -- Difference is handled upstream (engine tier skips parse_lua_surface etc.).
+        checks = {
+            { name = "H1",             pattern = "^#%s+%S" },
+            { name = "Badges",         pattern = "\n%*%*Lib%-ID:%*%*%s*lib%-" },
+            { name = "Topology",       pattern = "\n##%s+Topology[%s\n]" },
+            { name = "Topology-Block", pattern = "<!%-%-%s*topology:start" },
+            { name = "API",            pattern = "\n##%s+API[%s\n]" },
+            { name = "References",     pattern = "\n##%s+References[%s\n]" },
+        }
+        -- Engine-tier: relax the Badges check (engine uses "Version", "License" etc.
+        -- instead of a "Lib-ID:" prefix — engine is not a lib).
+        if tier == "engine" then
+            checks[2] = { name = "Badges", pattern = "\n%*%*[%w%-]+:%*%*" }
+        end
     end
 
     for _, c in ipairs(checks) do
@@ -175,10 +195,18 @@ function M.validate_readme_structure(markdown_string, tier)
         end
     end
 
-    -- Order check: API must appear before References in source order
+    -- Order check: for module tier Demonstrates must precede References
-    local api_pos = string.find(markdown_string, "\n##%s+API[%s\n]")
+    -- (no API exists to check); for non-module tiers API must precede References.
-    local ref_pos = string.find(markdown_string, "\n##%s+References[%s\n]")
+    local order_ok
-    local order_ok = (api_pos and ref_pos and api_pos < ref_pos) or (not api_pos and not ref_pos)
+    if tier == "module" then
+        local dem_pos = string.find(markdown_string, "\n##%s+Demonstrates[%s\n]")
+        local ref_pos = string.find(markdown_string, "\n##%s+References[%s\n]")
+        order_ok = (dem_pos and ref_pos and dem_pos < ref_pos) or (not dem_pos and not ref_pos)
+    else
+        local api_pos = string.find(markdown_string, "\n##%s+API[%s\n]")
+        local ref_pos = string.find(markdown_string, "\n##%s+References[%s\n]")
+        order_ok = (api_pos and ref_pos and api_pos < ref_pos) or (not api_pos and not ref_pos)
+    end
 
     return { missing_sections = missing, section_order_ok = order_ok }
 end