fix(job_key): keep the bare basis for an empty title whose URL has no six-digit run (#523)

The mixed-script rule from #514 appended the digest to `basis` as well,
so an empty title with a URL that carries no six-digit run moved from
"acme_https-example-com-jobs-abc-xyz" to "..._5ca8c6". Unreachable from
/scrape, which always passes a title, but a key is a pure function of the
posting and should not move for a case the rule was never about.

A lossy fragment still takes the digest; an empty title keeps the bare
basis or "untitled-<hash>" exactly as before #514. One new case pins the
pre-#514 output and fails on current master. The CHANGELOG example for
the Python-разработчик key is corrected to its real digest (python-fb29d7).

Follow-up suggested in the #514 merge note.

tools/job_key.py

@@ -146,7 +146,10 @@ def make_key(company: str, title: str, url: str = "") -> str:
             # is left to key on.
             digest_basis = str(url) if url else str(title)
             digest = hashlib.sha1(digest_basis.encode("utf-8")).hexdigest()[:HASH_LEN]
-            title_slug = f"{fragment or basis or 'untitled'}-{digest}"
+            # A lossy fragment needs the digest to tell two postings apart; an
+            # empty title keeps the bare basis (a URL-derived slug, or
+            # "untitled-<hash>") exactly as before the fragment rule existed.
+            title_slug = f"{fragment}-{digest}" if fragment else (basis or f"untitled-{digest}")
     return f"{company_slug}_{title_slug}"