Listing <project>/{archive,working,staging,reviewing}/ when the folder
doesn't exist on disk now returns an empty 200 listing instead of 404.
The stage-strip nav links into these folders unconditionally; without
this fallback, clicking "Working" against a fresh project (where
working/ hasn't been written to yet) lands on a 404 page rather than
a usable empty view.
Mechanism stays consistent with the existing lazy-folder design:
- GET on missing canonical folder → 200 + empty listing (this commit)
- first WRITE under the same path → EnsureCanonicalAncestors
materialises the on-disk folder + auto-own .zddc
reviewing/ stays virtual-only (in VirtualOnlyCanonicalNames); the
fallback just makes its empty listing always renderable. The future
reviewing/ aggregator (recorded in project memory) will replace the
empty listing with the join-computed virtual entries.
The fallback is gated on IsProjectRootFolder — only depth-2 paths
matching one of the four canonical names. Non-canonical missing paths
still 404 (TestListDirectory_NonCanonicalMissing_StillNotFound).
For working/ specifically the synthetic <viewer-email>/ home entry
still fires from virtualUserHomeEntry, so the user sees their own
placeholder even when working/ doesn't exist yet — first write into
that placeholder triggers the lazy-create chain.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>