fix: add explanatory comments to empty catch blocks in browser finder

[cxybd]

🐛 Problem

Empty catch blocks in browser path finding functions silently swallow errors without explanation:

try {
  const path = which.sync(name);
  return path;
} catch (e) {}  // ❌ Why is this empty?

This makes the code:

• ❌ Unclear whether error swallowing is intentional
• ❌ Difficult to maintain and understand
• ❌ Potentially confusing for new contributors

---

✅ Solution

Add clear explanatory comments to document the intentional behavior:

} catch (e) {
  // which.sync() throws when command not found - this is expected
  // when Chrome is not installed on the system. Continue trying other methods.
}

The comments clarify:

1. Why the exception is caught (command not found)
2. When this happens (browser not installed)
3. What happens next (continue with other detection methods)

---

📝 Changes

Files modified:

• packages/agent-infra/browser/src/browser-finder/chrome-paths.ts
• packages/agent-infra/browser/src/browser-finder/firefox-paths.ts

What changed:

• Added 3-line explanatory comments to each empty catch block
• No functional changes - behavior remains identical
• Improves code documentation and maintainability

Code diff:

  try {
    for (const name of list) {
      const path = which.sync(name);
      return path;
    }
  } catch (e) {
+   // which.sync() throws when command not found - this is expected
+   // when Chrome/Firefox is not installed on the system. Continue trying other methods.
  }

Statistics:

• Files changed: 2
• Lines added: 6 (comments only)
• Lines removed: 0
• Net change: +6 lines

---

🧪 Testing

• ✅ TypeScript compilation: Passes
• ✅ No functional changes: Behavior unchanged
• ✅ Code quality: Improved documentation

Expected behavior:

• Functions continue to work exactly as before
• Returns null when browser not found
• Upper layer BrowserFinder handles the null return appropriately

---

📊 Severity & Impact

Severity: Low-Medium (3-4/10)
Type: Code quality / Documentation improvement

Impact:

• ✅ Better code clarity - Intent is now explicit
• ✅ Easier maintenance - Future developers understand the logic
• ✅ Prevents confusion - Won't be mistaken for unintentional bug
• ✅ Follows best practices - Empty catch blocks should always have explanatory comments

Risk: None

• Only adds comments, no logic changes
• No breaking changes
• No new dependencies

---

🔍 Related Issues

Addresses empty catch blocks that could cause confusion during code review and maintenance. Improves code documentation following best practices.

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