fix(tests): one absent sister repo and the ratchet guarded nothing

tools/analyze_samples.py is a COMMITTED symlink into ../tidal-ears, which is
not cloned on the XPS24. rglob could see the path and read_text could not open
it, and _offenders() caught only SyntaxError — so a FileNotFoundError escaped
at import time and the whole module failed COLLECTION.

That is the exact failure this file exists to prevent, turned on itself: the
guard reported nothing rather than reporting a gap, and a guard that cannot run
guards nothing. Skip unreadable paths explicitly.

Verified standalone on the rig interpreter: 3 tests pass, 256 files scanned.

tools/tests/test_one_tidal_parser.py

@@ -122,6 +122,14 @@ def _offenders():
             tree = ast.parse(src)
         except SyntaxError:
             continue
+        except OSError:
+            # A path rglob can SEE but not READ: this repo commits symlinks to
+            # its sister projects (tools/analyze_samples.py -> ../tidal-ears/),
+            # and a box that has not cloned the sibling has a dangling one. That
+            # made the whole scan uncollectable — one absent sister repo and the
+            # ratchet guarded NOTHING, silently, which is the failure mode this
+            # file exists to prevent in the first place.
+            continue
         lines = src.splitlines()
         for lineno, value in _string_constants(tree):
             if not _looks_like_tidal_regex(value):