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

README.md

@@ -782,7 +782,7 @@ It also says when the binary is a development build, not a release.
 ## Configuration
 
 The config file is YAML. `vaultik config init` writes one to start from, and
-[`config.example.yml`](config.example.yml) is a longer example.
+[`configs/config.example.yml`](configs/config.example.yml) is a longer example.
 
 A command refuses to start when the config does not load. These commands are the
 exceptions:
@@ -1300,7 +1300,8 @@ is a trimmed, encrypted copy of the local index.
 
 These documents give the detail:
 
-- [`ARCHITECTURE.md`](ARCHITECTURE.md) describes how the code is organised.
+- [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) describes how the code is
+  organised.
 - [`docs/DATAMODEL.md`](docs/DATAMODEL.md) describes the local index.
 - [`docs/REPOSTRUCTURE.md`](docs/REPOSTRUCTURE.md) describes the layout of the
   destination.
@@ -1486,7 +1487,7 @@ built reproducibly.
 
 ## TODO
 
-Planned work is listed in [`TODO.md`](TODO.md).
+Planned work is listed in [`docs/TODO.md`](docs/TODO.md).
 
 ## license