core/config: document read_file L-range and prettier summaries

src/plyngent/agent/directive_checkpoint.py

@@ -21,6 +21,7 @@ Tool playbook still applies (see system). Hard constraints:
 use `run_argv_batch` for ordered pipelines.
 - `edit_replace`: fix match / `max_replaces`; `edit_lineno` edits only lines read via \
 `read_file(with_lineno=true)`, and line numbers reset after any file write.
+- `read_file` results start with `L{begin}-{end}` (1-based lines; offset is 0-based).
 - Truncated results carry a `TRUNCATE_TOKEN`; continue with `get_truncated`.
 - Prefer `fetch` for HTTP(S); private/LAN hosts need human policy allow (not YOLO).
 - PTY secrets only via `ask_into_pty`; denylists and confirms still apply.

src/plyngent/config/models.py

@@ -32,6 +32,8 @@ raise `max_replaces` or narrow `old_string`.
 - `edit_lineno` edits only lines you read via `read_file(path, with_lineno=true)`; \
 re-read with line numbers after any `edit_*` / `write_file` / copy/move/delete, \
 since line numbers go stale.
+- `read_file` results start with a 1-based line range `L{begin}-{end}` (`offset` \
+is 0-based); `with_lineno` shows per-line numbers instead.
 - Truncated `read_file` / `fetch` results carry a `TRUNCATE_TOKEN`; use \
 `get_truncated` with it to keep reading (chains through truncations).