fix: resolve ENOENT error with dynamic shell path detection (#3)

- Add dynamic bash detection using 'which bash' command
- Fallback to common paths: /bin/bash, /usr/bin/bash, /usr/local/bin/bash
- Ultimate fallback to /bin/sh for maximum compatibility
- Log detected shell path on startup for debugging
- Update CLAUDE.md with commit message guidelines

Fixes issue #3 where command execution failed with "spawn /bin/bash ENOENT"
when the cwd was set to invalid shell syntax like "~".

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

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

CLAUDE.md

@@ -287,4 +287,5 @@ You always have to push the changes into the git reposiroty. Before pushing chan
  - always update the issue which you works on
  - always add label to the issue if no label added
  - always write comment with the current status of the work 
+ - when you create commit message, mention the issue if exists
 

src/commandExecutor.js

@@ -1,12 +1,39 @@
 /**
  * Command executor for webhook events
  */
-import { exec } from 'child_process';
+import { exec, execSync } from 'child_process';
 import { promisify } from 'util';
 import logger from './logger.js';
 
 const execAsync = promisify(exec);
 
+// Detect shell path at module load time
+function detectShellPath() {
+  try {
+    // Try to find bash using 'which' command
+    const bashPath = execSync('which bash', { encoding: 'utf8' }).trim();
+    if (bashPath) {
+      return bashPath;
+    }
+  } catch (error) {
+    // Fallback to common bash locations
+    const commonPaths = ['/bin/bash', '/usr/bin/bash', '/usr/local/bin/bash'];
+    for (const path of commonPaths) {
+      try {
+        execSync(`test -x ${path}`, { encoding: 'utf8' });
+        return path;
+      } catch {
+        continue;
+      }
+    }
+  }
+  // Ultimate fallback: use /bin/sh
+  return '/bin/sh';
+}
+
+const SHELL_PATH = detectShellPath();
+logger.info('Detected shell path', { shell: SHELL_PATH });
+
 export class CommandExecutor {
   /**
    * Extract variables from webhook payload
@@ -173,7 +200,7 @@ export class CommandExecutor {
       const { stdout, stderr } = await execAsync(fullCommand, {
         timeout,
         cwd: cwd || process.cwd(),
-        shell: '/bin/bash',
+        shell: SHELL_PATH,
         maxBuffer: 10 * 1024 * 1024 // 10MB
       });