fix(lsp): Fix LSP server attachment and JSON parsing issues

- Replace lspconfig.scl_lsp registration with vim.lsp.start() + FileType autocmd
  for Neovim 0.11+ compatibility
- Fix Lua reserved keyword 'end' in tables (use bracket notation ['end'])
- Fix JSON decoder pattern matching bugs (s:find -> s:sub:match)
- Add LSP method name conversion (textDocument/didOpen -> textDocument_didOpen)
- Handle request vs notification correctly (only respond to requests with id)
- Strip CRLF line endings for Windows compatibility
- Add semantic token handler aliases
- Update documentation with implementation notes

AGENTS.md

@@ -104,6 +104,19 @@ function M.clear_cache()
 end
 ```
 
+## Lua Reserved Keywords
+
+Lua reserved keywords (like `end`, `for`, `in`, etc.) cannot be used as table keys directly. Use bracket notation:
+```lua
+-- WRONG: causes syntax error
+local range = { start = pos1, end = pos2 }
+
+-- CORRECT: use bracket notation
+local range = { start = pos1, ["end"] = pos2 }
+```
+
+This is especially important for LSP range objects which require an `end` field per the LSP specification.
+
 ## Error Handling
 
 ### Return Pattern
@@ -166,3 +179,34 @@ Find the last `:=`, `=>`, `=`, `<>`, `>=`, `<=`, `>`, `<`, `AND`, `OR`, `NOT` an
 | `:SCLMultilineParams` | Fill multiline parameters for FB/Function call |
 | `:LspSCLFormat` | Format current SCL file |
 | `:SCLGeneratePlcJson` | Generate plc.data.json from data_types/ |
+
+## LSP Server Implementation Notes
+
+### Method Name Conversion
+LSP methods like `textDocument/didOpen` are converted to handler names like `textDocument_didOpen`:
+```lua
+local method_name = message.method:gsub("/", "_")
+local handler = handlers[method_name]
+```
+
+### Request vs Notification
+- Requests have `id` field and require a response
+- Notifications have no `id` and should not receive a response
+```lua
+if message.id then
+  -- Only send response for requests
+  return { id = message.id, result = result }
+end
+```
+
+### Line Ending Handling
+The LSP server strips CRLF (`\r\n`) line endings for Windows compatibility:
+```lua
+line = line:gsub("\r$", "")
+```
+
+### JSON Parser
+The standalone JSON parser in `src/json.lua` handles:
+- Objects, arrays, strings, numbers, booleans, null
+- Escape sequences in strings
+- Whitespace skipping