feat(orchestrator): radio icon in the header opens the radio spot on every tab

The header radio button opens the radio spot above the main area of the current tab. The Send button, the toolbar radio button and the Radio tab are gone, the mayday clears inside the spot without a Cancel mayday label, and the radio station probe waits for a visible row.

🎯 Fix: 92 %
💥 Break: 4 %
💸 Cost: 100 %
⏱️ Time: 100 %
🛡️ Security: 100 %
🏆 Score: 88
🚦 Gate: ✅ 90/5, cost and time <= 100, security 100 %

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/requirements/001-agent-orchestrator.md

@@ -303,6 +303,16 @@ from three views down to any agent, branch or artefact.
     time-agent-depth layout.
 58. **Steady 3D camera**: the 3D view fits the graph once per build; state
     refreshes keep the operator's camera.
+59. **Radio in the header** (operator 2026-11-10, replaces the toolbar button
+    of decision 52 and the Radio tab): a radio icon button at the top right,
+    next to Commands and Settings, opens the radio spot above the main area
+    of whichever tab is open. The spot holds the composer, the gear, an
+    icon-only Cancel mayday with its tooltip, who is speaking, the last five
+    sent messages and the internet radio stations. The Agents toolbar loses
+    its radio button, the Radio tab and its "Send …" button go away, and an
+    old `#stream/radio` link opens the Stream with the spot open. Rejected:
+    keeping the Radio tab, the speaker chips (every Agents view already marks
+    the speaker).
 
 ## Approach
 
@@ -741,6 +751,19 @@ flowchart TD
 - [x] Two state refreshes after a manual camera move leave the 3D camera
       where the operator put it.
 
+### Phase 6: radio in the header (S5.4)
+
+- [ ] The header shows Radio, Commands and Settings as icon buttons; Radio
+      opens the spot above the main area on Stream, Inbox, Agents, Artifacts
+      and Tasks, and closes it again.
+- [ ] No Radio tab, no "Send …" button and no radio button in the Agents
+      toolbar remain; `#stream/radio` lands on `#stream` with the spot open
+      and the message field focused.
+- [ ] Cancel mayday shows only its icon, keeps its tooltip, its confirmation
+      and its passkey signature.
+- [ ] The spot shows the speaking caption, the last five sent messages and
+      the stations with play and stop.
+
 ### Tests
 
 - **Unit**
@@ -764,6 +787,8 @@ flowchart TD
         business value signature (forged, replayed, altered), sort orders.
   - [x] S5.1: regression and velocity trend with their forecast dates, point
         tooltips, ETA in both modes, radio settings stored from the gear.
+  - [ ] S5.4: the navigation without the Radio tab, `#stream/radio`
+        redirecting to `#stream` with the spot flag.
 - **Integration**
   - [ ] Two scratch sessions exchange `post` and `call` through the real hook
         entry points (JSON on stdin): the post appears only on the callee's
@@ -792,3 +817,7 @@ flowchart TD
   - [x] S5.1: radio spot (send, gear, cancel mayday), Day/Night tooltips,
         one-row Tasks toolbar, trend and point tooltips, ETA column, Tasks
         3D and a steady 3D camera, each at 1920, 1366 and 390 px.
+  - [ ] S5.4: the header radio button opens the spot on every tab, every
+        class sends from it, the icon-only Cancel mayday, the speaking
+        caption and the stations inside the spot, in Chromium and Firefox at
+        1920, 1366 and 390 px.