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The remaining in-scope handlers in this router read and write profile
documents inline on the ASGI event loop:
- GET /api/profiles/{name}/soul reads SOUL.md
- PUT /api/profiles/{name}/soul atomic_write_text(SOUL.md)
- PUT /api/profiles/{name}/description write_profile_meta(profile.yaml)
- GET /api/profiles/{name}/desktop-overlay reads desktop.json
The persona save is the sharpest of the four: atomic_write_text() writes a
temp file, fsyncs it and replaces the original, so the loop is parked for
however long the filesystem takes to durably commit — unbounded on a slow
or contended disk, and paid on every Save in the editor.
Each handler keeps its existing status-code mapping. The reads probe and
load in a single executor hop rather than two, which also avoids widening
the gap between the existence check and the read.
Both readers return a _MISSING sentinel rather than None for an absent
file. desktop.json may legitimately contain the document `null`; collapsing
that onto None would newly report an existing-but-empty overlay as absent.
The same distinction is what the SOUL.md durability tests rely on, where
"file missing" and "file empty" must not both read as never-set.
_resolve_profile_dir() stays on the loop in all four, as it does in the
rest of this sweep: it is a name check plus one stat, and it owns the
400/404 responses.