fix(gateway): repair and optimize lookahead bracket class in MEDIA regex

[InphinitiZ]

Summary

There is a critical escaping issue in the MEDIA: regex lookahead character class in gateway/platforms/base.py:

(?=[\\s`"',;:)\\\\\\]}]|$)

Inside a raw Python string, \\\] resolves to \\\] which represents an escaped backslash \\\\ and then a raw closing bracket ]. This prematurely closes the character class compilation, rendering any subsequent characters (like } or a second ]) completely outside the character class. As a result, paths inside parens or brackets like MEDIA:/tmp/test.png) would fail to extract correctly on the gateway.

Fix

Relocate the closing bracket ] (and trailing curly brace }) to the very beginning of the character class directly after [:

(?=[]}\\s`"',;:)\\\\]|$)

This is the standard and safest regex practice for including closing brackets inside character classes without triggering compile-time escapes or premature closures. All unit tests pass locally.

[teknium1]

This looks implemented on current main via the later consolidated MEDIA extraction work.

Automated hermes-sweeper review evidence:

• gateway/platforms/base.py:1232 now defines the shared MEDIA_TAG_CLEANUP_RE, with delimiter handling for ), ], and }, and compiles it with re.IGNORECASE at gateway/platforms/base.py:1237.
• A direct check on current main confirms BasePlatformAdapter.extract_media() extracts MEDIA:/tmp/test.png), MEDIA:/tmp/test.png], MEDIA:/tmp/test.png}, plus wrapper forms like (MEDIA:/tmp/test.png) / [MEDIA:/tmp/test.png] / {MEDIA:/tmp/test.png}.
• The real MEDIA extraction cluster was consolidated in 781604ce4c (fix(gateway): unify MEDIA: extraction extension set + close the unknown-ext black hole (#34517) (#34844)).
• The later linked discussion in fix(gateway): match uppercase media extensions in MEDIA: pattern #32695 notes that fix(gateway): repair and optimize lookahead bracket class in MEDIA regex #29620's bracket-class premise did not reproduce, and maintainer comments on fix(gateway): add re.IGNORECASE to MEDIA tag regex patterns #30535/fix(gateway): match MEDIA tags with case-insensitive file extensions #30722 point to fix(gateway): unify MEDIA: extraction extension set + close the unknown-ext black hole (#34517) #34844 as the superseding fix.

Thanks for surfacing this; it helped identify the MEDIA regex cluster that was fixed on main.