sbbuilder: list the default manifests, and keep them on the first edit

The helper replaces its default [manifests] table with the file's, so
adding one manifest to a file without the table dropped neovim's, and
the page showed no rows for the default that was in effect. With no
table in the file the page now lists the helper's defaults, and the
first add, remove or URL edit writes them all before its own change.
Toml.js gains sections(), to tell a missing table from an empty one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/desktop/modules/sbbuilder/README.md b/desktop/modules/sbbuilder/README.md
index 73bfe51..ddb5b75 100644
--- a/desktop/modules/sbbuilder/README.md
+++ b/desktop/modules/sbbuilder/README.md
@@ -19,7 +19,11 @@ Both follow the settings window's draft rules (`desktop/README.md`). A field
 is typed after its default: lists are words split on spaces (a list entry
 holding a space is a `ponytail:` ceiling: edit the file), numbers are
 range-checked. An emptied manifest URL holds Save back rather than unsetting
-the key, which would remove the row being typed in. The desktop defaults are
+the key, which would remove the row being typed in. The helper takes a
+`[manifests]` table whole, in place of its default one, so a file without
+one lists the helper's default rows, and the first add, remove or edit
+writes them all first: adding one row once silently dropped the default
+neovim manifest. The desktop defaults are
 copied from sb-builder's `config.py`, a `ponytail:` ceiling in `Sbb.qml`;
 the VM ones come from the helper.