feat(plugin): replace Lspsaga with native LSP & Snacks integration

Why: Clean up the heavy Lspsaga UI and adopt built‑in LSP plus Snacks for better performance and maintainability.

- New Features
  - Use native `vim.lsp.buf` functions for code actions, diagnostics, rename, etc.
  - Integrate Snacks picker for definitions, references, symbols, and type definitions.
- Enhancements  - Update keybindings to use Snacks and native APIs instead of Lspsaga.
  - Drop `nvimdev/Lspsaga.nvim`, `typescript-tools.nvim`, and unused `plenary.nvim`.
  - Preserve mini.misc auto‑root and other minor improvements.
- Bug Fixes
  - Resolve broken Lspsaga UI configuration and related mappings.
  - Remove stale `<leader>la` mapping that referenced Lspsaga.

plugin/mini.lua

@@ -25,8 +25,6 @@ require("mini.files").setup({
 })
 
 require("mini.misc").setup({
-	-- restore cursor position on file reopen
-	require("mini.misc").setup_restore_cursor(),
 	-- automated change of current directory
 	require("mini.misc").setup_auto_root(),
 })