Say when a session is working, and what it was told

Three things a phone could not see, all of them the same shape: the
session was doing something and nothing on screen said so.

A turn nobody here started never reported itself. `Running` was sent
where a message was *sent*, so a session picked up mid-turn, one
compacting on its own, or one another agent wrote to sat there reading
as idle until it finished. The driver now says it from what it observes
-- output that could only come from a turn in flight -- which is the
same set of events that already announced a steer, with the ends
swapped.

An imported session had it worse: nothing but replayed lines ever
reaches it, and a status was not among them, so it was permanently
whatever it was when it was adopted. Its file does not record a turn
ending, but it does record why each assistant message stopped, and
`tool_use` versus anything else answers it. A record that says nothing
leaves the status alone rather than voting for idle.

Messages from other agents were dropped outright: the CLI marks them
meta, and this replayed everything except meta. They are now a row of
their own, closed by default like a tool call, named for the session
that sent it -- not the reader's own bubble, because they did not say
it, and a session working on something this phone never asked for is
exactly what one of these explains.

Measured against a real session file rather than guessed: the peer
record carries the sender's name and the message body in `origin`,
beside a copy wrapped for the model to read.

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

@@ -109,6 +109,18 @@ val runningColor: Color
 val failedColor: Color
     @Composable get() = MaterialTheme.colorScheme.error
 
+/**
+ * Working on the conversation rather than in it: a compaction.
+ *
+ * Its own colour because it is its own kind of busy. Everything else a session does is progress
+ * through the task; this is the session rewriting what it remembers, it can take minutes, and
+ * nothing it produces appears in the transcript until it is over. A reader who has learned that
+ * blue means "not stuck, but not answering you either" has learned the only thing that
+ * distinguishes it from a session that has hung.
+ */
+val compactingColor: Color
+    @Composable get() = Mocha.Blue
+
 /** Waiting on a person: a question, a permission, a turn that is theirs. */
 val awaitingColor: Color
     @Composable get() = Mocha.Peach