Point links at the moved documents and config example

ARCHITECTURE.md, TODO.md and config.example.yml moved to docs/ and
configs/ on next. README.md now links to the new paths. docs/ARCHITECTURE.md
and the roadmap in docs/TODO.md link to their sibling documents by file
name, as docs/DATAMODEL.md and docs/REPOSTRUCTURE.md already do. The help
text and configs/config.example.yml name none of the old paths.

Model: fable-5-1

docs/TODO.md

@@ -25,9 +25,9 @@ Work planned after 1.0, loosely ordered by priority.
 
 - **Outside security audit.** Before 1.0 the encryption and blob-generation code
   was reviewed. Every bug the review found was fixed. The risks it accepted are
-  listed in [Accepted risks](docs/REPOSTRUCTURE.md#accepted-risks). No outside
-  audit has been done. age, zstd and content-defined chunking are mostly
-  off-the-shelf pieces. The code that joins them needs an outside read:
+  listed in [Accepted risks](REPOSTRUCTURE.md#accepted-risks). No outside audit
+  has been done. age, zstd and content-defined chunking are mostly off-the-shelf
+  pieces. The code that joins them needs an outside read:
     - key handling
     - recipient parsing
     - manifest trust boundary
@@ -74,7 +74,6 @@ Work planned after 1.0, loosely ordered by priority.
 - **Schema migrations after 1.0.** Migrations are supported, but none are added
   before 1.0 because there is no installed base yet. After 1.0, each schema
   change is a new migration, so an existing local index is migrated when
-  `vaultik` is updated. See
-  [`docs/DATAMODEL.md`](docs/DATAMODEL.md#schema-migrations).
+  `vaultik` is updated. See [`DATAMODEL.md`](DATAMODEL.md#schema-migrations).
 - **Storage backend coverage tests.** S3, `file://` and `rclone://` all share
   the `Storer` interface, but the rclone path is the least exercised in CI.