docs: encourage adding comments; fix nested IF/ELSIF indentation

- Update AGENTS.md to encourage comments instead of forbidding them
- Add docstrings to all public functions in src/ modules
- Add module headers and function comments to lua/scl/ modules
- Fix formatter to properly indent multi-line IF/ELSIF conditions
- Fix FB call detection to not match IF statements with parentheses

src/json.lua

@@ -1,5 +1,11 @@
+-- JSON Encoder/Decoder for LSP server
+-- Minimal implementation supporting basic JSON parsing and encoding
+
 local json = {}
 
+--- Check if a table is an array (sequential numeric keys starting from 1)
+--- @param t table Table to check
+--- @return boolean True if table is an array
 local function is_array(t)
   local i = 0
   for _ in pairs(t) do
@@ -11,6 +17,9 @@ local function is_array(t)
   return true
 end
 
+--- Escape special characters in string for JSON
+--- @param s string String to escape
+--- @return string Escaped string
 local function escape(s)
   s = s:gsub("\\", "\\\\")
   s = s:gsub('"', '\\"')
@@ -20,6 +29,9 @@ local function escape(s)
   return s
 end
 
+--- Encode Lua value to JSON string
+--- @param data any Value to encode
+--- @return string JSON string
 function json.encode(data)
   local t = type(data)
   if t == "nil" then
@@ -48,6 +60,10 @@ function json.encode(data)
   end
 end
 
+--- Skip whitespace in string
+--- @param s string JSON string
+--- @param i number Current position
+--- @return number New position after whitespace
 local function skip_whitespace(s, i)
   while i <= #s and s:sub(i, i):match("%s") do
     i = i + 1
@@ -55,6 +71,11 @@ local function skip_whitespace(s, i)
   return i
 end
 
+--- Parse JSON string literal
+--- @param s string JSON string
+--- @param i number Current position (at opening quote)
+--- @return string|nil Parsed string
+--- @return number New position
 local function parse_string(s, i)
   local result = {}
   i = i + 1
@@ -86,6 +107,11 @@ local function parse_string(s, i)
   return nil, i
 end
 
+--- Parse JSON number
+--- @param s string JSON string
+--- @param i number Current position
+--- @return number Parsed number
+--- @return number New position
 local function parse_number(s, i)
   local start = i
   if s:sub(i, i) == "-" then
@@ -114,6 +140,11 @@ end
 
 local parse_value
 
+--- Parse JSON array
+--- @param s string JSON string
+--- @param i number Current position (at opening bracket)
+--- @return table|nil Parsed array
+--- @return number New position
 local function parse_array(s, i)
   local arr = {}
   i = i + 1
@@ -136,6 +167,11 @@ local function parse_array(s, i)
   return nil, i
 end
 
+--- Parse JSON object
+--- @param s string JSON string
+--- @param i number Current position (at opening brace)
+--- @return table|nil Parsed object
+--- @return number New position
 local function parse_object(s, i)
   local obj = {}
   i = i + 1
@@ -205,6 +241,10 @@ parse_value = function(s, i)
   end
 end
 
+--- Decode JSON string to Lua value
+--- @param s string JSON string
+--- @return any|nil Parsed value
+--- @return number|nil Position after parsing or error
 function json.decode(s)
   if type(s) ~= "string" then
     return nil, "invalid input"