Dict show: comma after symbol-valued key changes the key on reload #11

From the Codex whole-repo review on #5 (review comment).

Location: imp-show.mts:104 on main (6813323)

[P2] Emit dictionary symbol values without changing their keys

When a dictionary contains symbol values, the inserted comma is attached directly to the key, but the loader's backtick-symbol regex accepts commas as part of symbol names. For example, showing :[c d] produces :[c, d]; evaluating that output creates a dictionary keyed by c, rather than c. Symbol-vector values have the same problem. Consequently, copying the displayed dictionary or round-tripping it through the serializer silently changes its keys. Emit a representation that the loader parses with the original key names.

Checked 2026-10-29: still present on main; not touched by open PRs #3, #4 or #7.