fix(web-ui): pixel loading language, tool-row sweep, composer polish

- StateDot ongoing: gradient spin ring replaced by an 8-cell pixel chase
  (2px matrix cells, stepped trail, no tweening)
- Chat: streaming pulse block replaced by a turn-level 4-pixel chase at the
  flow tail — rides the whole running turn (first-token wait, tools,
  streaming) instead of flickering with partial presence
- Tool rows (ToolRow/BashRow): running no longer swaps the icon for a dot;
  an animated mask band sweeps the row content, gliding off on exit via
  mask-position transition
- Composer: send/stop unified on the blue fill (bigger stop glyph, static
  white arrow), textarea box-sizing overflow fix, settling phase hides the
  composer while replay decides hero vs docked, workspace-placeholder
  fallback disables the bar
- Hero: glow moved behind (z-index) with lower opacity; tool-row hover icon
  crossfade at 100ms

packages/client/ui-conversation/tests/chat-code-subcalls.spec.tsx

@@ -251,7 +251,7 @@ describe('run_code sub-calls through the real chat machinery', () => {
     const b = await bench(snapshotWith([], dispatches, [runningCode(parent)]))
     const view = mountApp(b.slots)
     // The nested row derives 'running' from the RunningToolCall shape — the
-    // same StateDot ring a native in-flight row wears.
+    // same data-state chrome (row sweep) a native in-flight row wears.
     const nested = view.container.querySelector('[data-subcalls] [data-variant][data-state="running"]')
     expect(nested).not.toBeNull()
   })

packages/client/ui-conversation/tests/chat-tool-row.spec.tsx

@@ -125,12 +125,12 @@ describe('ToolRow', () => {
     expect(view.getByText('List files')).toBeTruthy()
   })
 
-  it('running and error states replace the icon with a StateDot', () => {
+  it('running keeps the icon (row sweep carries the signal); error swaps in a StateDot', () => {
     const runningView = render(<ToolRow {...rowProps} state="running" />)
-    expect(runningView.queryByTestId('tool-icon')).toBeNull()
+    expect(runningView.queryByTestId('tool-icon')).not.toBeNull()
     expect(runningView.container.querySelector('[data-state="running"]')).not.toBeNull()
     const errorView = render(<ToolRow {...rowProps} state="error" />)
-    expect(errorView.queryByTestId('tool-icon')).toBeNull()
+    expect(errorView.container.querySelector('[data-testid="tool-icon"]')).toBeNull()
   })
 
   it('non-expandable rows render a passive leading slot', () => {

packages/client/ui-conversation/tests/coverage-tails.spec.tsx

@@ -76,7 +76,7 @@ describe('tails', () => {
     expect(view.container.querySelector('[data-state="ok"]')).not.toBeNull()
   })
 
-  it('BashRow shows StateDot chrome for running/error/stopped (root session arm)', () => {
+  it('BashRow carries data-state for running (row sweep) and StateDots for error/stopped (root session arm)', () => {
     const sid = 'root-1' as SessionId
     const list = createSnapshotStore<SessionListState>({
       ids: [sid],