If you use your web-browser's built-in Developer Tools to Inspect the HTML generated for your title tagged passage you will notice that Harlowe 2.x adds passage tags to both the tw-story and tw-passage elements, and not to each individual markup/macro based link.
You need to change your CSS selectors to take the above fact into considerations.
tw-story[tags~="title"] tw-link, tw-story[tags~="title"] .enchantment-link {
color: #17174F;
}
tw-story[tags~="title"] tw-link:hover, tw-story[tags~="title"] .enchantment-link:hover {
color: navy;
}
note: I used the ~= (contains) operator instead of the = (equals) operator because a passage may have more than a single tag assigned to it.