docs: document host notices, restart resume, and /btw scope

AGENTS.md

@@ -110,8 +110,9 @@ Click app + readline REPL. Entry: `plyngent` / `python -m plyngent`.
 
 - **`plyngent chat`**: provider/model (flags or interactive; Tab via readline in `prompting`); sessions store `provider_name`/`model` and restore on resume; SQLite via `[database]` (file DB under user data when url unset; explicit `url = ":memory:"` kept + warn); workspace-bound; resume latest for cwd/`--workspace` by default (`--new` / `--session`). One-shot: `-p/--prompt` and non-TTY stdin; exit codes 0/1/2/3; `--yes` (YOLO on), `--auto-continue` (auto-raise limits), `--stream/--no-stream`, `--quiet`. Root `--log-level`. Enabled `[mcp]` servers start before the REPL (`_start_mcp_manager`, per-server failures warn on stderr) and are closed on exit (`McpManager.aclose`).
 - Slash: Click group in `cli/slash.py` + `awaitlet` for async work; Tab completer from registry + ParamType `shell_complete`. Multiline `"""` … `"""`; `/edit` via `$VISUAL`/`$EDITOR` (blocking only). `/yolo on|off|once` for soft destructive confirms. `/model --persist` / `/models --persist` write model catalog entries into TOML. `/todos` for human show/push/pop/clear of the todo stack. `/mcp` (`list` default) prints per-server status/tool counts + an `instructions` preview when the server sent usage guidance, + last stderr lines; `/mcp reconnect` re-reads config, restarts every enabled server, and rebuilds the tool registry. `/grants` lists directory-access grants (`revoke <index|all>`; config grants point at the TOML); `/status` includes the grant count.
-- `/btw` side questions: forked session; main transcript/DB untouched. `--tools=read` (default) exposes only `READ_ONLY` tools under `read_only_context()` (fetch=GET) with the main session view; `--tools=no` off; `--tools=full` whole-registry clone with fresh session. Tools off: default falls back to no tools; explicit `read`/`full` errors.
-- Explicit `/resume` or `--session` from another workspace prompts: **keep** / **update** / **abort**.
+- `/btw` side questions: forked session; main transcript/DB untouched. `--tools=read` (default) exposes only `READ_ONLY` tools under `read_only_context()` (fetch=GET) with the main session view; `--tools=no` off; `--tools=full` whole-registry clone with fresh session. Tools off: default falls back to no tools; explicit `read`/`full` errors. The model gets an `aside` notice as its last message before the question (unsaved exchange + tool scope), shown to the user as `[notice] aside: …`.
+- Explicit `/resume` or `--session` from another workspace prompts: **keep** / **update** / **abort**. A session resumed by a **freshly started process** (`--session` / default latest) also gets a `resume` notice about what a restart drops (PTY sessions, running commands, temp workspaces) — resuming inside a live process pushes nothing.
+- Host notices (`agent/notices.py`): system-level messages appended as trailing `developer` rows, never system-prompt edits — `Notice.to_message()` for the model, `.summary` for the user via `cli.display.echo_notice` (`--quiet` hides the user line only). Durable hosts persist them (`ChatAgent.push_notice`); a side agent without memory keeps its notice local. Trailing developer messages never end a turn, so `/retry` still sees an interrupted turn behind a notice or checkpoint.
 - Failed/cancelled turns: user kept; **committed tool rounds kept** (side effects not re-run on `/retry`); only unfinished assistant rolled back; Ctrl+C cancels; TTY confirms off-loop; auto-retry waits 5s/10s/15s/20s then +10s (10 attempts) and the budget **resets when an attempt completes a model round** (connection recovered); then `/retry`.
 - Pretty tool lines: known tools (`read_file`, `run_argv`, `grep_files`, …) print their `* Verb 'target' ` prefix as the call starts and append the outcome (`L1-4 (done)`, `(exit code 0)`) when the result lands, so a blocking tool stays visible while it runs. Interactive TTY only (`interactive_terminal()`): piped/plain output and `--verbose` keep whole lines / `[tool ok]`. A second call before the first result (parallel batch) erases the open prefix and falls back to whole lines.
 - **`plyngent providers`**, **`config path|edit`**. Config open: `$VISUAL`/`$EDITOR` (wait), else system default (`xdg-open` / `open` / `startfile`, non-blocking). `/edit` stays blocking-only. No providers → optional edit then reload when waited.

README.md

@@ -221,7 +221,7 @@ plyngent chat --session 3
 | `--auto-continue` | Auto-raise tool/PTY limits without prompting (like answering `yyy`) |
 | `--log-level` | On the root CLI: `DEBUG`, `INFO`, `WARNING`, … |
 
-Sessions resume the **most recently updated** session for the current workspace unless you pass `--new` or `--session`. Each session remembers the last **provider** and **model** (restored on resume so you are not re-prompted).
+Sessions resume the **most recently updated** session for the current workspace unless you pass `--new` or `--session`. Each session remembers the last **provider** and **model** (restored on resume so you are not re-prompted). A session resumed by a fresh `plyngent` process also gets a `[notice] resume: …` line: the model is told that process-scoped state — PTY sessions, running commands, temporary workspaces — did not survive the restart, and that an unfinished turn may have been cut off. The notice is kept with the transcript; `--quiet` hides only the user-facing line.
 
 When a tool-loop or PTY limit is hit, the prompt accepts `y` (continue once), `n` (stop), or `yyy` — **stop asking for the rest of this turn** (the next user turn prompts again). `--auto-continue` / `[agent] auto_continue_limits = true` skip the prompt for every turn.
 
@@ -266,7 +266,7 @@ Type `/help` in the REPL for the live list. Common ones:
 | `/yolo [on\|off\|once]` | Soft destructive confirms: sticky skip, off, or next turn only |
 
 | `/retry` | Re-run incomplete last user turn (after error/cancel) |
-| `/btw [--tools read\|no\|full] [--fresh]` | Side question without changing the main session (read-only tools by default) |
+| `/btw [--tools read\|no\|full] [--fresh]` | Side question without changing the main session (read-only tools by default; the model is told the exchange is unsaved and how its tools are scoped) |
 | `/provider` `/model` | Switch without restarting |
 | `/model --persist` | Save current model id into `plyngent.toml` catalog |
 | `/models` | List config + remote `GET /models` (always re-fetches) |