feat(integration): production-ready .version_history priority

- Change get_info() priority: .version_history first, merkwerk fallback
- Add read_version_history() for production deployment compatibility
- Works without merkwerk binary (tar.gz deployments)
- Maintains development fallback to merkwerk command

Production-ready: tar.gz deployments work without merkwerk installation.

integrations/lua-api.lua

@@ -70,6 +70,67 @@ local function parse_json_response(json_str)
     return data
 end
 
+-- Read latest entry from .version_history file
+local function read_version_history()
+    local file = io.open(".version_history", "r")
+    if not file then
+        return nil, "No .version_history file found"
+    end
+
+    local last_line = nil
+    for line in file:lines() do
+        -- Skip comment lines
+        if not line:match("^%s*#") and line:match("%S") then
+            last_line = line
+        end
+    end
+    file:close()
+
+    if not last_line then
+        return nil, ".version_history contains no valid entries"
+    end
+
+    -- Parse: content_hash,vcs_hash,branch,timestamp,author,vcs_type,project_type
+    local parts = {}
+    for part in last_line:gmatch("([^,]+)") do
+        table.insert(parts, part)
+    end
+
+    if #parts < 7 then
+        return nil, "Invalid .version_history format"
+    end
+
+    -- Get base version from VERSION file if available
+    local base_version = "?.?.?"
+    local version_file = io.open("VERSION", "r")
+    if version_file then
+        local version_content = version_file:read("*line")
+        if version_content and not version_content:match("^%s*$") then
+            base_version = version_content:match("^%s*(.-)%s*$")
+        end
+        version_file:close()
+    end
+
+    -- Build response in same format as merkwerk
+    local data = {
+        project_name = parts[7] and parts[7]:gsub("-api$", "") or "unknown", -- lua-api → lua
+        project_type = parts[7] or "unknown",
+        base_version = base_version,
+        content_hash = parts[1] or "unknown",
+        full_version = base_version .. "+" .. (parts[1] or "unknown"),
+        version = base_version .. "+" .. (parts[1] or "unknown"),
+        timestamp = parts[4] or "",
+        vcs = {
+            type = parts[6] or "none",
+            hash = parts[2] or "",
+            branch = parts[3] or ""
+        },
+        source = "version_history"
+    }
+
+    return data, nil
+end
+
 -- Generate fallback info when merkwerk is unavailable
 local function fallback_info()
     return {
@@ -96,7 +157,7 @@ local function is_cache_valid(ttl)
     return cache.data and (current_time - cache.timestamp) < ttl
 end
 
--- Get version information with caching
+-- Get version information with NEW priority order
 function merkwerk.get_info(options)
     options = options or {}
     local use_cache = options.cache ~= false
@@ -117,66 +178,73 @@ function merkwerk.get_info(options)
         return result
     end
 
-    -- Execute merkwerk command
+    -- PRODUCTION PRIORITY: Try .version_history FIRST
+    local history_data, history_error = read_version_history()
+    if history_data then
+        -- Success: Use version history data
+        if include_build_info then
+            history_data.build_info = {
+                cached = false,
+                source = "version_history",
+                method = "production_ready"
+            }
+        end
+
+        -- Update cache
+        if use_cache then
+            cache.data = history_data
+            cache.timestamp = os.time()
+        end
+
+        return history_data
+    end
+
+    -- FALLBACK: Try merkwerk command (development/testing)
     local json_result, error_msg = execute_merkwerk("info --json")
+    if json_result then
+        local data = parse_json_response(json_result)
+        if data then
+            data.source = "merkwerk"
 
-    if not json_result then
-        -- merkwerk failed - use fallback
-        local fallback = fallback_info()
-        if fallback_version then
-            fallback.base_version = fallback_version
-            fallback.full_version = fallback_version .. "+unknown"
-        end
-        if error_msg then
-            fallback.error = error_msg
-        end
+            if include_build_info then
+                data.build_info = {
+                    cached = false,
+                    source = "merkwerk_command",
+                    method = "development_fallback",
+                    history_error = history_error
+                }
+            end
 
-        if include_build_info then
-            fallback.build_info = {
-                cached = false,
-                error = error_msg or "merkwerk unavailable"
-            }
-        end
+            -- Update cache
+            if use_cache then
+                cache.data = data
+                cache.timestamp = os.time()
+            end
 
-        return fallback
+            return data
+        end
     end
 
-    -- Parse JSON response
-    local data = parse_json_response(json_result)
-    if not data then
-        -- JSON parsing failed - use fallback
-        local fallback = fallback_info()
-        fallback.error = "Failed to parse merkwerk JSON output"
-
-        if include_build_info then
-            fallback.build_info = {
-                cached = false,
-                error = "JSON parsing failed",
-                raw_output = json_result:sub(1, 100)  -- First 100 chars for debugging
-            }
-        end
-
-        return fallback
+    -- LAST RESORT: Pure fallback
+    local fallback = fallback_info()
+    if fallback_version then
+        fallback.base_version = fallback_version
+        fallback.full_version = fallback_version .. "+unknown"
     end
 
-    -- Add metadata
-    data.source = "merkwerk"
+    fallback.error = "Both version_history and merkwerk failed"
 
     if include_build_info then
-        data.build_info = {
+        fallback.build_info = {
             cached = false,
-            timestamp = os.time(),
-            cache_ttl = cache_ttl
+            source = "fallback",
+            method = "emergency_fallback",
+            history_error = history_error,
+            merkwerk_error = error_msg or "merkwerk unavailable"
         }
     end
 
-    -- Update cache
-    if use_cache then
-        cache.data = data
-        cache.timestamp = os.time()
-    end
-
-    return data
+    return fallback
 end
 
 -- Get only the content hash (lightweight)