Say which half of the wait a llama turn is in

A turn has two waits in front of the first token and they were one word.
`SessionStatus::Loading` was already the model coming off disk; this adds
`SessionStatus::Reading` for llama-server processing the prompt -- emitted when
the request goes out, cleared by the first thing the model says of any kind, so
it covers every generate in a tool loop rather than only the first.

Prefill is the expensive half on this machine: measured 9.5s for 6,068 tokens
and 22s for 14,068 on the 27B with the GPU to itself. Reported as `running`
that was indistinguishable from a model thinking, which is the thing the reader
is waiting for. The phone draws both with the working spinner and its own
words -- "loading model" and "reading prompt" -- and the session screen's
status row now spins for all three busy states instead of only `running`,
which is also how `loading` stops being a bare word with nothing moving.

Measured while checking the tok/s figure, and recorded in the rigs skill: the
27B holds 55.5 to 50.3 tok/s between 1.5k and 14k of context, so decode decays
gently, while the 0.6B on the CPU falls 30.1 to 11.5 over 6k. A shared GPU is a
different failure -- the model does not load at all.

Verified on the emulator against a real llama session: "loading model" while
the server started, then "reading prompt" with the spinner through prompt
processing, then the thinking card.

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

server/src/session/driver.rs

@@ -658,6 +658,20 @@ pub enum SessionStatus {
     /// state -- a driver that reports it is responsible for holding what it
     /// is sent until it can deliver it -- but this is what says so on screen.
     Loading,
+    /// The model is reading what it was given, and has not begun answering.
+    ///
+    /// Its own state for the same reason [`SessionStatus::Loading`] is, one
+    /// level down: prompt processing is work the machine does before a turn
+    /// produces anything, and on a long conversation it is the part of the
+    /// wait somebody is looking at. Reported as `Running` it was
+    /// indistinguishable from a model thinking, which is what the reader is
+    /// actually waiting to see.
+    ///
+    /// It is still a turn in progress -- nothing settles, nothing is invited
+    /// -- and it is not a measurement of the prompt: it says the request is
+    /// out and the model has said nothing yet, which for a server serving one
+    /// slot is what reading the prompt looks like.
+    Reading,
     /// The session's own turn is over, but work it started is still going:
     /// a backgrounded subagent, or a command left running.
     ///

server/src/session/llama/mod.rs

@@ -1588,6 +1588,12 @@ fn generate(
         map.insert(key.clone(), value.clone());
     }
 
+    // Prompt processing starts the moment this is sent and nothing comes back
+    // until it is done, so this is where the wait somebody is watching begins.
+    // Cleared by the first thing the model says, whatever kind it is.
+    shared.emit(Event::Status {
+        state: SessionStatus::Reading,
+    });
     let mut response = ureq::post(format!("{endpoint}/v1/chat/completions"))
         .config()
         // A turn can be long: a slow model on a long prompt, and the whole
@@ -1627,6 +1633,9 @@ fn generate(
     // timestamps. `None` between blocks -- a turn can think, speak, call a
     // tool and think again.
     let mut thinking: Option<std::time::Instant> = None;
+    // Whether the model has produced anything at all yet; until it has, this
+    // turn is still reading its prompt.
+    let mut speaking = false;
     // What the server says its own generation ran at. Read from it rather than
     // divided out of the wall time here, which would count the request, the
     // prompt processing and this loop's own scheduling as generation.
@@ -1672,6 +1681,12 @@ fn generate(
         let Some(delta) = chunk.pointer("/choices/0/delta") else {
             continue;
         };
+        if !speaking && says_something(delta) {
+            speaking = true;
+            shared.emit(Event::Status {
+                state: SessionStatus::Running,
+            });
+        }
         if let Some(fragment) = delta.get("reasoning_content").and_then(Value::as_str)
             && !fragment.is_empty()
         {
@@ -1717,6 +1732,26 @@ fn generate(
     Ok(Reply { text, calls })
 }
 
+/// Whether a delta carries anything the model produced, of any kind.
+///
+/// The first one of these is the end of prompt processing. The chunk that only
+/// opens the message -- `{"role": "assistant", "content": null}` -- is not one,
+/// which is why this asks what is *in* the delta rather than that one arrived.
+fn says_something(delta: &Value) -> bool {
+    let said = |key| {
+        delta
+            .get(key)
+            .and_then(Value::as_str)
+            .is_some_and(|text| !text.is_empty())
+    };
+    // Not `is_some`: a dialect that sends the key as an explicit null on every
+    // chunk would end prompt processing on the one that opens the message.
+    let calling = delta
+        .get("tool_calls")
+        .is_some_and(|calls| !calls.is_null());
+    said("content") || said("reasoning_content") || calling
+}
+
 /// How long one completion may take before the turn is abandoned.
 const GENERATE_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(1800);