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/coding-agent/src/core/prompt-templates.ts

@@ -1,7 +1,7 @@
 import { existsSync, readdirSync, readFileSync, statSync } from "fs";
 import { homedir } from "os";
 import { basename, dirname, isAbsolute, join, resolve, sep } from "path";
-import { CONFIG_DIR_NAME, getPromptsDir } from "../config.js";
+import { CONFIG_DIR_NAME } from "../config.js";
 import { parseFrontmatter } from "../utils/frontmatter.js";
 import { createSyntheticSourceInfo, type SourceInfo } from "./source-info.js";
 
@@ -175,14 +175,14 @@ function loadTemplatesFromDir(dir: string, getSourceInfo: (filePath: string) =>
 }
 
 export interface LoadPromptTemplatesOptions {
-	/** Working directory for project-local templates. Default: process.cwd() */
-	cwd?: string;
-	/** Agent config directory for global templates. Default: from getPromptsDir() */
-	agentDir?: string;
-	/** Explicit prompt template paths (files or directories) */
-	promptPaths?: string[];
-	/** Include default prompt directories. Default: true */
-	includeDefaults?: boolean;
+	/** Working directory for project-local templates. */
+	cwd: string;
+	/** Agent config directory for global templates. */
+	agentDir: string;
+	/** Explicit prompt template paths (files or directories). */
+	promptPaths: string[];
+	/** Include default prompt directories. */
+	includeDefaults: boolean;
 }
 
 function normalizePath(input: string): string {
@@ -204,11 +204,11 @@ function resolvePromptPath(p: string, cwd: string): string {
  * 2. Project: cwd/{CONFIG_DIR_NAME}/prompts/
  * 3. Explicit prompt paths
  */
-export function loadPromptTemplates(options: LoadPromptTemplatesOptions = {}): PromptTemplate[] {
-	const resolvedCwd = options.cwd ?? process.cwd();
-	const resolvedAgentDir = options.agentDir ?? getPromptsDir();
-	const promptPaths = options.promptPaths ?? [];
-	const includeDefaults = options.includeDefaults ?? true;
+export function loadPromptTemplates(options: LoadPromptTemplatesOptions): PromptTemplate[] {
+	const resolvedCwd = options.cwd;
+	const resolvedAgentDir = options.agentDir;
+	const promptPaths = options.promptPaths;
+	const includeDefaults = options.includeDefaults;
 
 	const templates: PromptTemplate[] = [];