feat(scarfmon,chat): Phase 3b — dampen finalize bursts + Thinking… status + wider loadConfig stack

Three targeted fixes from the Phase 3a baseline.

Bubble-burst dampening (Phase 3b-1):
- RichChatViewModel.finalizeStreamingMessage wraps both the
  streaming-id rewrite and the empty-finalize remove() in a
  no-animation Transaction. The id flip from 0 → permanent value
  was the load-bearing trigger of the 5–8 RichMessageBubble.body
  fires we were seeing 1–2 ms after every `finalizeStreamingMessage`
  interval; SwiftUI ran an animated diff against neighbors and
  re-evaluated their bodies. The new message is content-equal to
  the streaming one — there is no animation worth running.

Thinking… status promotion (Phase 3b-2):
- RichChatViewModel exposes `isStreamingThoughtsOnly` — true while
  a turn is in flight, has emitted thought-stream bytes, and has not
  yet produced any visible assistant text. The Phase 3a baseline
  showed this is where most of the user-perceived "feels slow" lives:
  reasoning models commonly take 3–8 s before producing visible
  output, and Scarf surfaced no specific signal during that window.
- Mac ChatView.displayedStatus promotes the toolbar pill to
  "Thinking…" when the flag is true.
- iOS connectionBanner gains a transient "Thinking…" strip with
  spinner, same trigger condition.

Phase 3a fix-up:
- HermesFileService.loadConfig stack-trace logging widened from
  one frame to a 10-frame window prefixed with "#N", so the actual
  caller is visible past inlined ScarfMon wrappers (the prior log
  surfaced ScarfMon.measure itself, not the loadConfig caller).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/Scarf iOS/Chat/ChatView.swift

@@ -400,7 +400,21 @@ struct ChatView: View {
                 showSpinner: false
             )
         default:
-            EmptyView()
+            // v2.7: surface "Thinking…" while the agent's thought
+            // stream is in flight without any visible message bytes.
+            // Hermes reasoning models commonly take 3–8 s here and
+            // the streaming bubble has nothing to render — the user
+            // would otherwise see a stalled transcript. Disappears
+            // the moment the first message chunk arrives.
+            if controller.vm.isStreamingThoughtsOnly {
+                connectionBannerStrip(
+                    text: "Thinking…",
+                    tint: ScarfColor.info,
+                    showSpinner: true
+                )
+            } else {
+                EmptyView()
+            }
         }
     }