refactor(lsp): remove duplicate LSP tools already provided by OpenCode

Remove lsp_goto_definition, lsp_find_references, lsp_symbols as they
duplicate OpenCode's built-in LspGotoDefinition, LspFindReferences,
LspDocumentSymbols, and LspWorkspaceSymbols.

Keep oh-my-opencode-specific tools:
- lsp_diagnostics (OpenCode lacks pull diagnostics)
- lsp_servers (server management)
- lsp_prepare_rename / lsp_rename (OpenCode lacks rename)

Clean up associated dead code:
- Client methods: hover, definition, references, symbols, codeAction
- Utils: formatLocation, formatSymbolKind, formatDocumentSymbol, etc.
- Types: Location, LocationLink, SymbolInfo, DocumentSymbol, etc.
- Constants: SYMBOL_KIND_MAP, DEFAULT_MAX_REFERENCES/SYMBOLS

-418 lines removed.

src/tools/index.ts

@@ -1,7 +1,4 @@
 import {
-  lsp_goto_definition,
-  lsp_find_references,
-  lsp_symbols,
   lsp_diagnostics,
   lsp_servers,
   lsp_prepare_rename,
@@ -56,9 +53,6 @@ export function createBackgroundTools(manager: BackgroundManager, client: Openco
 }
 
 export const builtinTools: Record<string, ToolDefinition> = {
-  lsp_goto_definition,
-  lsp_find_references,
-  lsp_symbols,
   lsp_diagnostics,
   lsp_servers,
   lsp_prepare_rename,