fix: Improve navigate_page_history error messages

[mithun50]

Problem

The navigate_page_history tool previously suppressed all
navigation errors with a generic message: "Unable to
navigate {back|forward} in currently selected page." This
provided no context about why the navigation failed, making
it difficult for users to understand whether:

• No page exists in the history
• A timeout occurred
• Some other error happened

Solution

Enhanced error handling to provide specific, actionable
feedback:

1. Check navigation result: Capture the return value
   from goBack()/goForward() to detect when navigation is
   impossible
2. No history detection: When result is null, return:
   "Cannot navigate back, no previous page in history."
3. Timeout errors: Show duration: "Navigation back timed
   out after 30000ms."
4. Other errors: Include actual error message instead of
   generic text

Changes

• Modified navigate_page_history handler in
  src/tools/pages.ts
• Added result checking for null (no history available)
• Enhanced error messages with specific context
• Improved debugging experience for users

Testing

• Verify "no previous page" message when navigating back on
  first page
• Verify "no next page" message when navigating forward at
  end of history
• Confirm timeout errors show duration
• Ensure other errors display actual error messages

[mithun50]

Fixes: #259