fix(coding-agent): remove process-cwd tool singletons and use tool-name allowlists

- switch SDK/CLI tool selection to name-based allowlists
- apply allowlists across built-in, extension, and SDK tools
- remove ambient process.cwd defaults from core tooling and resource helpers
- update tests, examples, and TUI callers for explicit cwd plumbing
- add regression coverage for extension tool filtering

closes #3452
closes #2835

packages/tui/src/autocomplete.ts

@@ -265,11 +265,7 @@ export class CombinedAutocompleteProvider implements AutocompleteProvider {
 	private basePath: string;
 	private fdPath: string | null;
 
-	constructor(
-		commands: (SlashCommand | AutocompleteItem)[] = [],
-		basePath: string = process.cwd(),
-		fdPath: string | null = null,
-	) {
+	constructor(commands: (SlashCommand | AutocompleteItem)[] = [], basePath: string, fdPath: string | null = null) {
 		this.commands = commands;
 		this.basePath = basePath;
 		this.fdPath = fdPath;