Distinguish qBittorrent and Cleanuparr pattern syntax in README

qBittorrent's excluded file names field uses Qt glob wildcards only.
The regex: prefix is supported by Cleanuparr's Malware Blocker but
not by qBittorrent. Split the Pattern syntax section into two
subsections documenting each consumer's capabilities and recommend
wildcards as the safe default for all entries.

README.md

@@ -125,25 +125,44 @@ rules and worked examples.
 
 ## Pattern syntax
 
-Each line in `blacklist` and `whitelist` is a pattern in one of the
+The patterns in `blacklist` and `whitelist` are consumed by two different
-following forms (the same forms that qBittorrent's excluded file names
+tools with different capabilities. Use only the common subset (wildcards)
-accepts, since that is where blacklist patterns end up via Cleanuparr's
+to ensure patterns work everywhere.
-Blocklist Sync):
 
-| Form | Example | Matches |
+### qBittorrent (via Blocklist Sync)
+
+qBittorrent's excluded file names field uses Qt glob wildcards:
+
+| Pattern | Example | Matches |
 |---|---|---|
-| `*example` | `*.srt` | File name ends with `example` |
+| `*` | `*.srt` | Zero or more characters |
-| `example*` | `sample*` | File name starts with `example` |
+| `?` | `*.r??` | Exactly one character |
-| `*example*` | `*sample*` | File name contains `example` |
+| `[abc]` | `*.[rs]00` | One character from the set |
-| `example` | `RARBG.txt` | File name is exactly `example` |
+| `[a-z]` | `*.[r-z]??` | One character in the range |
-| `regex:<regex>` | `regex:.*\.srt$` | File name matches the regex |
+| `[!abc]` | `*.[!m]??` | One character NOT in the set |
+| Literal | `VOSTFR` | Exact match |
+
+Regex, backslashes, and anchors (`^`, `$`, `\d`, `(?i)`) are **not
+supported** by qBittorrent and will be silently ignored.
+
+### Cleanuparr Malware Blocker (Sonarr/Radarr queue)
+
+Cleanuparr's Malware Blocker supports all the wildcard forms above plus
+regex with the `regex:` prefix:
+
+```
+regex:.*\.srt$
+```
+
+Regex patterns only work in Cleanuparr's Malware Blocker. They do not
+work when pushed to qBittorrent via Blocklist Sync.
+
+### Merge script
 
 The merge script subtracts the whitelist from the blacklist as **exact
 strings**, not by pattern semantics. To remove a pattern from the
 blacklist, the whitelist line must be byte-for-byte identical to the
-blacklist line. `*.srt` in the whitelist strips `*.srt` from the
+blacklist line. See
-blacklist; it does **not** strip `regex:.*\.srt$` even though both
-patterns describe the same files. See
 [Lists](https://git.hisp.no/arr/blocklists/wiki/Lists) for the full rules.
 
 ## Sync schedule