Workspace: a path with an empty segment is a second tree entry for the same disk file #471

What's wrong

parsePath (src/modules/workspace/index.ts, ~1715 on main e670363) returns the mount-relative path exactly as written. For example, work/sub//c.txt and work/sub/c.txt resolve to the same file on disk, so the traversal guard passes both. But they are two separate keys in the workspace tree. Chronicle's validate_tree_path refuses . and .. segments, but not empty ones.

Why it matters

The workspace can hold the same disk file under two keys:

• a push from one alias is refused with "disk changed since it was checked";
• the other alias goes stale and later reads as a conflict.

With #463's edit_many, this becomes an edit that never reaches disk, inside an answer that says every edit is stored (raised on #463 as R1-3).

How it was found

A scratch repro during the review of #463:

1. write work/sub//c.txt.
2. write work/sub/c.txt.
3. read work/sub//c.txt.

After these steps the tree lists both sub//c.txt and sub/c.txt.

Suggested fix

In parsePath, collapse empty segments, or refuse them, so that every spelling of a path maps to one key.

Found during our review of #463: #463 (review)

_{Posted by the maintainer's desk assistant.}