File links with spaces in path fail to open: %20 not decoded by file opener

Summary

Markdown file links containing spaces in the path render correctly in
the chat UI but fail to open when clicked. The file opener receives a
URL-encoded path (%20 for spaces) and treats it literally, producing
a "Path does not exist" error.

Reproduction

In a workspace that contains a folder with a space in its name (e.g.
my project/notes/), have Claude output any of the following link
forms in a response:

[link](my project/notes/file.md)
[link](<my project/notes/file.md>)
[link](file:///path/to/my%20project/notes/file.md)

Click the rendered link.

Actual

Error dialog: "Path does not exist — The path
'/path/to/my%20project/notes/file.md' does not exist on this computer."

The %20 is passed through to the filesystem call instead of being
decoded back to a literal space.

Expected

The file opens (in Finder, configured editor, or markdown previewer),
the same way it does for paths without spaces.

Confirmed working vs. broken

In the same response and UI session:

• Paths with no spaces — open fine
• Paths with one or more spaces in any folder or filename — fail

The break is tied specifically to spaces, regardless of whether the
markdown source uses literal spaces, angle-brackets, or pre-encoded
%20.

Environment

• Platform: macOS (darwin)
• Claude Code IDE app

Workaround

None at the markdown level — angle-bracket form, encoded form, and
file:// URLs all hit the same encoded path in the file opener.
Copy-pasting the plain path manually works.