feat: add gt and gb document navigation

docs/configuration.md

@@ -57,7 +57,7 @@ Key notation follows [Herdr's readable style](https://herdr.dev/docs/configurati
 
 Normal mode binds `ctrl+o` to `config.core.jump_back` and `ctrl+i`/`tab` to `config.core.jump_forward`. Insert-mode Tab remains literal text. Override or disable these keys with the ordinary per-mode binding interface; both jump actions also appear in the command palette.
 
-The built-in Normal `gf` sequence follows Markdown file links. It is not a configurable general sequence prefix: bind `config.core.follow_link` to a single key or leader sequence to add another route. A configured or disabled Normal `g`, or choosing `g` as the leader, overrides the built-in prefix.
+The built-in `gt`/`gb` sequences move to the first/last line in Normal and Visual; `gf` follows Markdown file links in Normal only. This is not a configurable general sequence prefix: bind `config.core.document_start`, `config.core.document_end`, or `config.core.follow_link` to a single key or leader sequence to add another route. A configured or disabled `g` overrides the built-in prefix in that binding mode; choosing `g` as the leader overrides it in both modes.
 
 ## Action reference
 
@@ -74,6 +74,7 @@ The built-in Normal `gf` sequence follows Markdown file links. It is not a confi
 | Normal, Visual | `select`, `select_linewise`, `search_next`, `search_previous` |
 | Normal, Visual | `repeat_last_edit` |
 | Normal, Visual | `file_picker`, `file_explorer` |
+| Normal, Visual | `document_start`, `document_end` |
 | Normal, Insert, Visual | `line_start`, `line_end` |
 | Normal, Insert, Visual, Tree | `left`, `right` |
 | Normal, Insert, Visual, Selection, Tree | `down`, `up` |