Order the session list by when each agent was turned on

A running session no longer moves: the ones with a process come first,
oldest start first, so starting one appends it to the bottom of that
group and nothing it goes on to do -- beginning a turn, finishing one,
asking a question -- can shift it. Sorting by activity with the
awaiting-answer ones floated to the top is what this replaces; the
status word and its colour already say which session wants something
without the row having to move to say it. Stopped sessions are a group
below, most recently active first.

The order is the server's: `SessionConfig::started` is written each time
a process is started for a session and reported as `started`, so it is
the same on every device and survives a backend restart -- which adopts
processes rather than starting them, and so could not work the times out
for itself. Applied on the phone, because presentation order is a
display decision.

`LiveSession::info` takes the session's config entry rather than a
parameter per field read from it, which is what `AutoResumeView` existed
to bundle; that goes.

Verified on the emulator against the sandbox: three echo sessions kept
their order while the newest-active one was messaged; a stopped and
restarted session moved below one started after it; a stopped session
dropped below every running one; and after a backend restart the
recorded times came back unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/Api.kt

@@ -225,6 +225,15 @@ data class SessionSummary(
     val usageProvider: String?,
     val status: String,
     val lastActivity: Double,
+    /**
+     * Epoch seconds a process was last started for this session -- when this agent was last turned
+     * on. What the list orders the running sessions by; see [sessionsInListOrder].
+     *
+     * The server's own, so the order is the same on every device and across a backend restart. An
+     * older server does not send it, and those sessions fall back to when the session was last
+     * active, which is the best this app can do without inventing a time.
+     */
+    val started: Double,
     /** Latest measured number of live background tasks; zero also covers older servers. */
     val backgroundTasks: Int,
     /**
@@ -265,6 +274,7 @@ private fun parseSession(session: JSONObject) =
         usageProvider = session.optString("usageProvider").ifEmpty { null },
         status = session.getString("status"),
         lastActivity = session.getDouble("lastActivity"),
+        started = session.optDouble("started", session.getDouble("lastActivity")),
         backgroundTasks = session.optInt("backgroundTasks", 0),
         subagents = session.optInt("subagents", 0),
     )