fix: batch A - crash bugs, a leak, and startup/edge fragility

Seven confirmed defects from the code audit, each small and low-risk.

* ai_functions.get_random_cyclic_message: random.randint(0, len(CYCLIC_WORDS))
  is inclusive -> could return len -> IndexError. Now randrange(len) + guard on
  an empty CYCLIC_WORDS.
* librarian_commands.get_image_sadox: random.randrange(0, len(res)-1) never
  picked the last comic and raised ValueError('empty range') on a single file.
  Now randrange(len) + an empty-dir guard.
* ai_commands image generation: every DALL-E error branch replied but did not
  return, so control fell through to `if response:` with response unbound ->
  UnboundLocalError right after the friendly message. Each branch now returns;
  response is pre-initialised; and PermissionDeniedError no longer passes a
  (message, text) tuple as a single arg.
* search_bot DOI match: `item["DOI"] in data` was a substring test, so a DOI
  that is a prefix of a longer one (10.1/1 vs 10.1/12) produced a false 'exists'
  hit. Now matches the line's first whitespace token exactly, via an O(1) dict
  index built once per consumer (also removes the O(queried-DOIs) per-line scan
  - a real win for large databases).
* communication_subroutine.scan_incoming: matched records were never removed
  from awaiting_q, so it grew unbounded over uptime and a reused UUID could
  re-match a stale record. Matched records are now dropped after dispatch.
* communication_subroutine.id3: (resp.headers.get("icy-name") or "").title()
  guards against a stream that omits headers (was AttributeError on None,
  500-ing the /prepped_tracks "next" handler).
* betoniarka.scan_tracks: waits for the radio logs to exist instead of dying
  with FileNotFoundError on a fresh deploy (which silently killed the
  now-playing forwarder until a restart).

Verified: tests/unit/test_search_bot.py gains exact-match and trailing-metadata
cases; full unit job 43 passed. Remaining observations (image-gen stale
/home/pi fallback paths + dead FileNotFoundError-after-OSError branch; tailer
still vulnerable to mid-run log rotation; DOI-first-token assumption) noted for
follow-up - none are crashes on the normal path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

conjurer_librarian/search_bot.py

@@ -148,8 +148,11 @@ def consumer(in_q, control_q, doi, live_results, result_list, control_dict, expe
     print(f"Consumer thread started: {no} no")
     empty_counter = 0
     alive_no = 0
+    # DOI -> result item, so a line is matched with one O(1) dict lookup instead
+    # of scanning every queried DOI. Items are shared with result_list, so
+    # setting exists here is seen by everyone.
+    doi_index = {item["DOI"]: item for item in result_list}
     while True:
-        done_check = True
         try:
             data = in_q.get(block=True, timeout = 1)
             if data is _sentinel:
@@ -161,16 +164,21 @@ def consumer(in_q, control_q, doi, live_results, result_list, control_dict, expe
                 alive_no += 1
                 print(f"C{no}__{alive_no}\r", end="")
 
-                for item in result_list:
-                    if item["DOI"] in data and not item["exists"]:
-                        print(f"HIT in {no} content {data[0]} line {data[1]} file {data[2]} {item['exists']}")
-                        _logger.info(data)
-                        _logger.info("HIT")
-                        item["exists"] = True
-                        live_results.append(item)
-                    done_check = done_check and item["exists"]
-                if done_check:
-                    control_q.put(_sentinel)
+                # Each DB line is a DOI (optionally followed by metadata). Match
+                # the WHOLE first token exactly - the old `item["DOI"] in data`
+                # was a substring test, so a DOI that is a prefix of a longer one
+                # (10.1/1 vs 10.1/12) produced a false 'exists' hit.
+                parts = data.split()
+                line_doi = parts[0] if parts else ""
+                item = doi_index.get(line_doi)
+                if item is not None and not item["exists"]:
+                    print(f"HIT in {no}: {line_doi}")
+                    _logger.info("HIT %s", line_doi)
+                    item["exists"] = True
+                    live_results.append(item)
+                    # All found? Signal producers to stop early (rare -> cheap).
+                    if all(it["exists"] for it in result_list):
+                        control_q.put(_sentinel)
         except Empty:
             empty_counter += 1
             time.sleep(1)