fix(frontend,harness): phase-stepper wiring, central tail, activity-panel markdown

- WorkflowBar: center the phase pills (add justify-center).
- tht-gate.js: the gate was sending the descriptive phase name (e.g.
  "chiarimento") instead of the workflow.yaml id ("F1") in the widget's
  `phase` field, so the frontend's F1..F8 match never hit and pills never
  lit up. Rename phaseName -> phaseId, return p.id.
- CentralStatus: expand the live "working" tail from a single truncated
  line to up to 5 lines (line-clamp-5 safety net for unbroken paragraphs).
- ModelActivityPanel: render the streamed tail through react-markdown +
  remark-gfm instead of raw per-line <p> tags, so emphasis/headings render
  and blank-line paragraph breaks (previously stripped) are preserved;
  tail-cut now operates on paragraphs instead of physical lines.

Updated tests accordingly (WorkflowBar/CentralStatus/ModelActivityPanel/
AppShell.session-mgmt); full frontend suite (98/98) + harness gate node
tests (34/34) + tsc -b pass.

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

frontend/src/shell/CentralStatus.tsx

@@ -2,10 +2,14 @@ import { useEffect, useReducer, useState } from "react";
 import { useSessionStore } from "../store/sessionStore";
 import { WorkingSpinner } from "./WorkingSpinner";
 
-/** Last few words of a string — a compact "what the model is doing now" tail. */
-function lastWords(s: string, n = 8): string {
-  const w = s.trim().split(/\s+/).filter(Boolean);
-  return w.slice(-n).join(" ");
+/** Last few non-blank lines of a string — a compact multi-line "what the model is
+ *  doing now" tail (mirrors ModelActivityPanel's tail-line logic, at a smaller size). */
+function tailLines(s: string, n = 5): string {
+  const lines = s
+    .split("\n")
+    .map((l) => l.trimEnd())
+    .filter((l) => l.trim() !== "");
+  return lines.slice(-n).join("\n");
 }
 
 /** The minimal central view: the user's last input/choice, a live "working" indicator
@@ -41,7 +45,7 @@ export function CentralStatus({
   if (!working && !lastUserEntry && stepMessages.length === 0) return null;
 
   const elapsed = startedAt ? Math.max(0, Math.floor((Date.now() - startedAt) / 1000)) : 0;
-  const tail = lastWords(transcript.at(-1)?.text ?? "");
+  const tail = tailLines(transcript.at(-1)?.text ?? "");
 
   return (
     <div className="flex flex-col gap-3">
@@ -55,19 +59,25 @@ export function CentralStatus({
       )}
 
       {working && (
-        <div className="flex min-w-0 items-center gap-2 text-sm text-muted-foreground">
-          <button
-            type="button"
-            onClick={onOpenActivity}
-            aria-label="Show model activity"
-            title="Model activity"
-            className="grid size-5 shrink-0 place-items-center rounded text-primary transition-colors hover:bg-muted"
-          >
-            <WorkingSpinner spinning className="size-3.5" />
-          </button>
-          <span className="shrink-0 tabular-nums">{elapsed}s</span>
-          {tail && <span className="min-w-0 truncate text-muted-foreground/70">· {tail}</span>}
-          <span className="sr-only">ThothII is working</span>
+        <div className="flex flex-col gap-1">
+          <div className="flex min-w-0 items-center gap-2 text-sm text-muted-foreground">
+            <button
+              type="button"
+              onClick={onOpenActivity}
+              aria-label="Show model activity"
+              title="Model activity"
+              className="grid size-5 shrink-0 place-items-center rounded text-primary transition-colors hover:bg-muted"
+            >
+              <WorkingSpinner spinning className="size-3.5" />
+            </button>
+            <span className="shrink-0 tabular-nums">{elapsed}s</span>
+            <span className="sr-only">ThothII is working</span>
+          </div>
+          {tail && (
+            <p className="line-clamp-5 whitespace-pre-wrap break-words pl-7 text-sm text-muted-foreground/70">
+              {tail}
+            </p>
+          )}
         </div>
       )}