CODE-067: subs.js reads an ODB failure as "no submodules"

Now: OPEN
Sev: LOW
Rep: ///bee
Ask: gritzko
Rev: ///bee#8cb69a0
See: BEE-026
See: CODE-042

Input

Context

index/subs.js:82-101 wraps the tree read in a bare catch (e) { return []; }, so a corrupt tree, an unreadable pack or a missing commit is indistinguishable from a repo without submodules: view/wtstat.js and stage.js quietly show and stage nothing. status.stageOf already carries a note for the same case. Found in the 2026-09-18 index review.

Goals

Return {mounts, err} and let the view say so, the way stageOf does.

WIP

Design decisions

mounts() -> { mounts, err }; err is the WHOLE sentence the view prints, as status.js stageOf carries its note.
A path that is no repo at all keeps the old silence (err ""); only an ODB that could not answer speaks up.
The HEAD tree is read in subs.js itself: submodulePaths spells an unreadable tree and a repo with no .gitmodules the very same way.
add/rm REFUSE on err rather than sweeping the parent alone; bee wts puts the words after both frames, so no column moves (be's CI-004).

TODOs

[v] repro: unreadable tree object, wtstat says nothing
[v] error surfaced

Blockers and bummers

sync.js (commit, merge follow) and done.js took the new shape mechanically only: those writers still read an ODB failure as "no mounts". Whether they should refuse is gritzko's call, not this ticket's.