chore: adjust README, AGENTS, and test runner for server-only scope

After splitting from the original scl_lsp repo, update documentation
and test infrastructure to reflect the server-only scope of this repo.

- README.md: focused on LSP server features, tree-sitter grammar,
  running the server, and Mason installation reference
- AGENTS.md: server-only project structure and conventions
- test/run_tests.lua: run only server tests (formatter, plc_json)

AGENTS.md

@@ -1,9 +1,6 @@
 # AGENTS.md - tia-lsp
 
-A Neovim/LazyVim plugin and standalone LSP server for Siemens TIA Portal languages. Currently supports **SCL**; planned support for STL/AWL, LAD, FBD. The project is split into two repos:
-
-- **`tia-lsp`** (this repo) — LSP server (`src/`) + tree-sitter grammar (`grammar.js`). Editor-agnostic.
-- **`tia-lsp.nvim`** — Neovim plugin (`lua/`) that launches the server and adds editor features.
+A standalone LSP server for Siemens TIA Portal languages. Currently supports **SCL**; planned support for STL/AWL, LAD, FBD. This repo is the server only (`src/` + tree-sitter grammar). The companion Neovim plugin lives in `tia-lsp.nvim`.
 
 ## Build/Lint/Test Commands
 
@@ -20,16 +17,11 @@ tree-sitter parse <file.scl>  # Parse single SCL file
 
 # Lua Linting
 luacheck src/                 # Lint LSP server code
-luacheck lua/tia/             # Lint plugin modules
 
-# Unit & Integration Tests
-lua test/run_tests.lua       # Run all tests
-lua test/test_udt.lua        # Run UDT parser tests
-lua test/test_db.lua         # Run DB parser tests
-lua test/test_fb.lua         # Run FB parser tests
+# Unit Tests
+lua test/run_tests.lua       # Run all server tests
 lua test/test_formatter.lua  # Run formatter tests
 lua test/test_plc_json.lua   # Run plc_json tests
-lua test/test_integration.lua # Run integration tests
 
 # Reference Project
 # Tests use files from: ~/dev/siemens/projects/scl_lang_support_lazyvim_ref_project/
@@ -49,38 +41,16 @@ tia-lsp/
 │   ├── plc_json.lua        # External UDT/DB loading (language-agnostic)
 │   ├── builtin_instructions.lua  # TIA Portal built-in types
 │   └── json.lua            # JSON encoder/decoder
-├── lua/tia/                 # Neovim plugin (uses require)
-│   ├── udt_parser.lua      # UDT parser
-│   ├── db_parser.lua       # Global DB parser
-│   ├── fb_parser.lua       # Function Block parser
-│   ├── variables.lua       # Variable extraction
-│   ├── workspace_types.lua # Workspace scanning
-│   ├── multiline_params.lua
-│   ├── auto_prefix.lua
-│   └── attr_toggle.lua
-├── lua/tia_lsp/             # Plugin entry point
-│   ├── init.lua            # Main plugin setup (vim.lsp.start)
-│   └── plugins/scl.lua     # LazyVim plugin spec
-├── queries/                 # Tree-sitter queries (per-language: queries/scl/)
-└── grammar.js               # Tree-sitter grammar (language name: 'scl')
+├── grammar.js               # Tree-sitter grammar (language name: 'scl')
+└── test/                    # Server tests
 ```
 
 ## Naming Convention
 
-- **Project name** (repo, Lua module, LSP server, mason package): `tia-lsp` / `tia_lsp` — umbrella for all TIA languages.
+- **Project name** (repo, LSP server, mason package): `tia-lsp` / `tia_lsp` — umbrella for all TIA languages.
 - **Language name** (filetype, tree-sitter parser, grammar): `scl` — stays as-is. Future languages (`stl`, `lad`, `fbd`) get their own names.
 - **LSP client name**: `tia_lsp` (one client handles all TIA languages; dispatches by `filetype` / `languageId`).
 - **Diagnostic source**: `tia_lsp`.
-- **Commands**: `:SCLFormat`, `:SCLShowVariables`, etc. — per-filetype prefix. Future: `:STLFormat`, etc.
-
-## Filetype Detection
-
-After the split, `ftdetect/scl.vim` will live in `tia-lsp.nvim`. Currently required in Neovim config:
-```vim
-au BufRead,BufNewFile *.scl set filetype=scl
-au BufRead,BufNewFile *.udt set filetype=scl
-au BufRead,BufNewFile *.db set filetype=scl
-```
 
 ## Code Style Guidelines
 
@@ -106,13 +76,10 @@ return M
 - Booleans: prefix with `is_`, `has_` (e.g., `is_udt`, `has_members`)
 
 ### Imports
-- `lua/tia/` modules: `require("tia.module_name")`
-- `lua/tia_lsp/` entry: `require("tia_lsp")`
 - `src/` modules: `dofile(script_path .. "/module.lua")`
 - External dependencies: wrap in `pcall()` for safety
 
 ### Code Formatting
-- `lua/tia/` and `lua/tia_lsp/`: 2 spaces indentation
 - `src/`: tab-based indentation
 - Max line length: 120 characters
 - No trailing whitespace
@@ -190,6 +157,5 @@ Use the reference project for testing:
 
 Contains `.scl`, `.db`, `.udt`, and `.xml` files for comprehensive testing of:
 - LSP features (hover, completion, go-to-definition)
-- Formatter (`:SCLFormat`)
-- Attribute block toggle
+- Formatter
 - Workspace type scanning