feat: typescript migration (#40)

* chore: initialize TypeScript configuration and build setup

- Add tsconfig.json for root and mcp-server with strict type checking
- Install typescript and @types/node as devDependencies
- Add npm build script for TypeScript compilation
- Update main entrypoint to compiled dist/shannon.js
- Update Dockerfile to build TypeScript before running
- Configure output directory and module resolution for Node.js

* refactor: migrate codebase from JavaScript to TypeScript

- Convert all 37 JavaScript files to TypeScript (.js -> .ts)
- Add type definitions in src/types/ for agents, config, errors, session
- Update mcp-server with proper TypeScript types
- Move entry point from shannon.mjs to src/shannon.ts
- Update tsconfig.json with rootDir: "./src" for cleaner dist output
- Update Dockerfile to build TypeScript before runtime
- Update package.json paths to use compiled dist/shannon.js

No runtime behavior changes - pure type safety migration.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: update CLI references from ./shannon.mjs to shannon

- Update help text in src/cli/ui.ts
- Update usage examples in src/cli/command-handler.ts
- Update setup message in src/shannon.ts
- Update CLAUDE.md documentation with TypeScript file structure
- Replace all ./shannon.mjs references with shannon command

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* chore: remove unnecessary eslint-disable comments

ESLint is not configured in this project, making these comments redundant.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/setup/environment.ts

@@ -9,7 +9,7 @@ import chalk from 'chalk';
 import { PentestError } from '../error-handling.js';
 
 // Pure function: Setup local repository for testing
-export async function setupLocalRepo(repoPath) {
+export async function setupLocalRepo(repoPath: string): Promise<string> {
   try {
     const sourceDir = path.resolve(repoPath);
 
@@ -34,7 +34,8 @@ export async function setupLocalRepo(repoPath) {
       await $`cd ${sourceDir} && git add -A && git commit -m "Initial checkpoint: Local repository setup" --allow-empty`;
       console.log(chalk.green('✅ Initial checkpoint created'));
     } catch (gitError) {
-      console.log(chalk.yellow(`⚠️ Git setup warning: ${gitError.message}`));
+      const errMsg = gitError instanceof Error ? gitError.message : String(gitError);
+      console.log(chalk.yellow(`⚠️ Git setup warning: ${errMsg}`));
       // Non-fatal - continue without Git setup
     }
 
@@ -46,11 +47,10 @@ export async function setupLocalRepo(repoPath) {
     if (error instanceof PentestError) {
       throw error;
     }
-    throw new PentestError(
-      `Local repository setup failed: ${error.message}`,
-      'filesystem',
-      false,
-      { repoPath, originalError: error.message }
-    );
+    const errMsg = error instanceof Error ? error.message : String(error);
+    throw new PentestError(`Local repository setup failed: ${errMsg}`, 'filesystem', false, {
+      repoPath,
+      originalError: errMsg,
+    });
   }
-}
+}