bug: results for show and ask posts with no link should link to the post itself

ShowHN posts do not require URLs in the link. If an item does not have a link then the search results include the link to the search itself, rather than either (1) linking to the post or (2) not having a link at all.
It doesn't do anything if left clicked, but right clicking opens the search again in another tab. This disrupts a practice of opening tabs to read while reading through search results because the user may not remember which result they were trying to look at.

Example query: [[Show HN: Search engine to quickly find in-depth articles from engineering blogs]](https://hn.trieve.ai/?q=Show+HN%3A+Search+engine+to+quickly+find+in-depth+articles+from+engineering+blogs&score_threshold=5&page_size=30&prefetch_amount=30&rerank_type=none&highlight_delimiters=+%2C-%2C_%2C.%2C%2C&highlight_threshold=0.85&highlight_max_length=50&highlight_max_num=50&highlight_window=0&recency_bias=0&highlight_results=true&use_quote_negated_terms=true&storyType=story&matchAnyAuthorNames=&matchNoneAuthorNames=&popularityFilters=%7B%7D&sortby=relevance&dateRange=all&searchType=fulltext&page=1&getAISummary=false)

Notice the top result.

Example posts:
without link: https://news.ycombinator.com/item?id=25763329

with link: https://news.ycombinator.com/item?id=40112958

Reproduce the example query and inspect how search results render links for Show HN posts with and without URLs. Confirm the result currently points to the search itself, then verify that a no-link post links to its Hacker News item or has no link, without changing behavior for posts that have URLs.

Written by the indexing model from the issue text.