Path canonicalization strips only one trailing separator: "/home/user/a//" stays "/home/user/a/" and IsChildOf("/home/user/a") returns true #308

What's wrong

SemanticPath.MakeCanonical removes at most one trailing directory separator. A path written with a doubled trailing separator keeps one, so it is not equal to the same directory written without it. The containment check then treats it as a child of itself.

Where

• Semantics.Paths/SemanticPath.cs:118-147: if (canonical.EndsWith(separator) && …) canonical = canonical[..^separator.Length];. This runs once and does not loop. The XML doc above it says "Removes trailing directory separators".
• Semantics.Paths/Utilities/PathContainment.cs:44-56 (from the IsChildOf/IsParentOf return false for every path directly under a filesystem root ("/home" vs "/", "C:\foo" vs "C:\") #282/IsChildOf/IsParentOf ignore case on Linux: "/home/user/DOCS/report" is reported as inside "/home/user/docs" #291 fixes) counts a longer path as strictly inside when it continues with a separator after the parent prefix.

Failure scenario

These were reproduced against the built library on Linux, .NET 10:

var a  = AbsoluteDirectoryPath.Create("/home/user/a//"); // canonical: "/home/user/a/"
var b  = AbsoluteDirectoryPath.Create("/home/user/a");   // canonical: "/home/user/a"
a == b                 // false
a.IsChildOf(b)         // true: a directory reported as inside itself

Doubled separators are common in paths built by string concatenation (dir + "/" + sub where dir already ends in /). Code that uses IsChildOf to guard against acting on the root of a tree, or to detect recursion, gets the wrong answer.

Suggested fix

• In MakeCanonical, trim all trailing separators, stopping at the root (/ or C:\). For example, TrimEnd(separator) and then restore the root if the result became empty or C:.
• Optionally, make PathContainment ignore a trailing separator on the child before comparing lengths, so it is robust on its own.
• Add tests: "/a//" equals "/a", IsChildOf is false for that pair, and "//" still canonicalizes to the root.