gitignore: drop the redundant bin/obj rules, unhide perl-meta sources

[Oo]bj/ and [Bb]in/ matched exactly what the **/obj/ and **/bin/ lines
above them already matched, so they only added noise. The capital-B form
had no directory in the fleet to match at all.

**/bin/ matches at any depth, which .NET output needs (src/<proj>/bin),
but it also swallowed perl-meta's perl/bin/Meta/ tree - 341 tracked Perl
sources. They kept working because ignore rules do not apply to tracked
files, but a NEW file there never showed up in git status, so it would be
silently left out of a commit. Negate that one path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CRamKn5DoUKKusg4mckH5L

Author: veltzer

.gitignore

@@ -146,10 +146,13 @@ build/
 .ipynb_checkpoints/
 
 # c#
+# **/obj/ and **/bin/ match at any depth, which is what .NET output needs
+# (src/<proj>/bin, src/<proj>/obj). The un-globbed [Oo]bj/ and [Bb]in/ that
+# used to follow were redundant with these two and are gone.
 **/obj/
 **/bin/
-[Oo]bj/
-[Bb]in/
+# perl-meta keeps real Perl sources under perl/bin/Meta/, not build output.
+!/perl/bin/
 
 # flash/air
 *.swf