Fix linting errors in a number of core and tool files (partial)

- As part of this work I also started building out errors.ts which will be a cumulation of error helpers to better handle the challenging `catch (error: unknown)` requirement.
- More changes are to come, this is truly a partial change in order to not disrupt as many people as possible.

Part of https://b.corp.google.com/issues/411384603

packages/cli/src/tools/glob.tool.ts

@@ -20,16 +20,11 @@ export interface GlobToolParams {
   path?: string;
 }
 
-/**
- * Result from the GlobTool
- */
-export interface GlobToolResult extends ToolResult {}
-
 /**
  * Implementation of the GlobTool that finds files matching patterns,
  * sorted by modification time (newest first).
  */
-export class GlobTool extends BaseTool<GlobToolParams, GlobToolResult> {
+export class GlobTool extends BaseTool<GlobToolParams, ToolResult> {
   /**
    * The root directory that this tool is grounded in.
    * All file operations will be restricted to this directory.
@@ -125,9 +120,9 @@ export class GlobTool extends BaseTool<GlobToolParams, GlobToolResult> {
       if (!fs.statSync(searchDirAbsolute).isDirectory()) {
         return `Search path is not a directory: ${shortenPath(makeRelative(searchDirAbsolute, this.rootDirectory))} (absolute: ${searchDirAbsolute})`;
       }
-    } catch (e: any) {
+    } catch (e: unknown) {
       // Catch potential permission errors during sync checks
-      return `Error accessing search path: ${e.message}`;
+      return `Error accessing search path: ${e}`;
     }
 
     // Validate glob pattern (basic non-empty check)
@@ -165,7 +160,7 @@ export class GlobTool extends BaseTool<GlobToolParams, GlobToolResult> {
    * @param params Parameters for the glob search
    * @returns Result of the glob search
    */
-  async execute(params: GlobToolParams): Promise<GlobToolResult> {
+  async execute(params: GlobToolParams): Promise<ToolResult> {
     const validationError = this.invalidParams(params);
     if (validationError) {
       return {