fix: render markdown links that include a title attribute

[masfour7]

Problem

Markdown links with a title attribute are not rendered — the raw syntax appears as plain text:

// Expected: a clickable "Click Here" link
// Actual: raw "[Click Here](https://foo.com \"page title\")" shown as text
GptMarkdown('[Click Here](https://foo.com "page title")');

This is valid CommonMark syntax. Reported in #122, fix approach described in #121.

Root Cause

Two issues in ATagMd inside lib/markdown_component.dart:

1. Regex too strict — the pattern [^\\s]* stops matching at the first space, so url "title" was never captured.
2. Title not stripped — even if the regex had matched, the raw title string would have been included in the URL passed to onLinkTap.

Fix

1. Broaden the regex to allow any character except ) inside the link parentheses:

// Before
RegExp get exp => RegExp(r"(?<!\!)[.*]\([^\s]*\)");

// After — [^)] allows spaces, quotes, anything except the closing paren
RegExp get exp => RegExp(r"(?<!\!)[.*?]\([^)]*\)");

2. Strip the title from the URL after extraction:

// Before
final url = text.substring(urlStart, urlEnd).trim();

// After
final rawUrl = text.substring(urlStart, urlEnd).trim();
// Strip optional title attribute: [text](url "title") or [text](url 'title')
final url = rawUrl.replaceFirst(RegExp(r'\s+["\'\'][^\"\'']*["\'\']\s*$'), '').trim();

The URL passed to onLinkTap is now clean with no title string appended.

Closes #122
Closes #121

[saminsohag]

This pull request contains issues in the code.