feat: Allow resuming previous AI sessions (#3407)

This PR introduces session continuation to Atuin AI.

* Conversations with Atuin AI are stored in a local SQLite database
* Upon startup, Atuin AI tries to find a session to resume based on its
directory/workspace and the time since the last event
* If found, Atuin AI will show a note that the session has been resumed,
and an event is added to help the LLM know where the invocation
boundaries are
* If not, Atuin AI will create a new conversation
* The user can create a new conversation with `/new`
* The new setting `ai.session_continue_minutes`, which defaults to `60`,
controls how old the last event in a session can be before it's no
longer considered for automatic resuming.

<img width="1055" height="593" alt="image"
src="https://github.com/user-attachments/assets/3f9ff01a-ef64-44a9-b0e2-3a4252c5746f"
/>

## Architecture

A new `SessionService` trait defines an API contract for a service that
can manage session data. `LocalSessionService` implements this, with
`DaemonSessionService` a possible future extension point.

`SessionManager` owns a `dyn SessionService` and delegates as
appropriate.

1 files changed, 3 insertions, 0 deletions

diff --git a/crates/atuin-ai/src/tui/view/turn.rs b/crates/atuin-ai/src/tui/view/turn.rs
index 7369f151..a2555dc6 100644
--- a/crates/atuin-ai/src/tui/view/turn.rs
+++ b/crates/atuin-ai/src/tui/view/turn.rs
@@ -170,6 +170,9 @@ impl<'a> TurnBuilder<'a> {
             } => {
                 self.add_out_of_band_output(name, command.as_deref(), content);
             }
+            ConversationEvent::SystemContext { .. } => {
+                // Not rendered in the TUI — only sent to the API
+            }
         }
     }