feat(nomos): per-session turn serialization + chat reliability/UX fixes

The agent could run two turns for one session at once (a reconnect resumed
while the live turn was still going), and their interleaved tool calls
corrupted the activity panel, fabricated a confusing "parallel/nested"
sequence, and made tasks feel stuck/never-ending. Several UX gaps compounded it.

Turn serialization (F1):
- turnGate: at most one in-flight turn per session. Background resume paths
  (continuation worker, idle sweep, answer-question, /resume, reconnect)
  skip non-blocking when busy; the live chat path waits briefly then bails
  cleanly instead of stacking a second turn.
- resumeSession returns whether it ran; continueSession marks an execution
  "continued" only after a real run (review P0) so a busy-skip can't lose a
  finished-execution result. Idle nudge bumps only after delivery (P1).

Connection state (F2/F3, web):
- humanize/bucket raw errors ("model connection dropped..."); one surface
  per drop; a terminal task.status event clears stuck streaming/disconnected
  state and dismisses the connection toast. Reconnect no longer spawns turns.

Streaming where you look (F4, web):
- live command output in the global activity timeline and in the inline
  tool card (auto-opened, tail-pinned) -- not just the per-window rail.

Other (web): artifact/knowledge deep links (F5); step-first stable
"thinking" headline (F6); stable chat layout, no empty->content reflow (F7);
lazy event sync (P2.2); reconnect skips a terminal session (P2.1).

VERSION: 0.14.2 -> 0.15.0

web/src/lib/components/ChatThread.svelte

@@ -17,6 +17,7 @@
   import { marked } from 'marked'
   import DOMPurify from 'dompurify'
   import type { ChatMessage } from '$lib/stores/chat'
+  import type { ToolCallResult } from '$lib/types'
   import type { SessionQuestion } from '$lib/api'
 
   let {
@@ -83,8 +84,15 @@
   const indicatorLabel = $derived.by(() => {
     if (error) return error
     if (!streaming && indicatorDone) return 'Done'
-    const running = $activityLogProp.find((e: ActivityEntry) => e.status === 'running')
-    if (running) return running.description
+    // Prefer the running PLAN STEP as the headline — it's stable across the
+    // step's many tool calls, so the line stops rewriting itself on every
+    // command (the "thinking overwrites itself" complaint, F6). Falls back to
+    // the current tool only when there's no active step (a plan-less Q&A or
+    // between steps), and to a plain "thinking…" otherwise.
+    const runningStep = $activityLogProp.find((e: ActivityEntry) => e.type === 'step_running')
+    if (runningStep) return runningStep.description
+    const runningTool = $activityLogProp.find((e: ActivityEntry) => e.type === 'tool_running')
+    if (runningTool) return runningTool.description
     return 'Agent is thinking…'
   })
 
@@ -195,6 +203,27 @@
     if (streaming) return
     onSend(q)
   }
+
+  // Merge live streaming output (from the activity log's `run` entry) onto the
+  // in-flight turn's tool calls so the inline tool card shows command output as
+  // it arrives — the place the operator naturally "checks the tool". Only the
+  // last assistant message can be streaming, so only it gets enriched; history
+  // is untouched (and has no live output anyway). (F4)
+  function toolsWithLive(
+    tools: ToolCallResult[],
+    entries: ActivityEntry[],
+    isLiveTurn: boolean
+  ): ToolCallResult[] {
+    if (!isLiveTurn) return tools
+    const liveById = new Map<string, string>()
+    for (const e of entries) {
+      if (e.liveOutput && e.id) liveById.set(e.id, e.liveOutput)
+    }
+    if (liveById.size === 0) return tools
+    return tools.map((t) =>
+      t.id && liveById.has(t.id) ? { ...t, liveOutput: liveById.get(t.id) } : t
+    )
+  }
 </script>
 
 <div class="flex h-full min-h-0 min-w-0 flex-col" bind:clientHeight={threadHeight}>
@@ -274,7 +303,7 @@
                    the text below it. -->
                   {#if msg.tools.length > 0 || traceStatus !== 'idle'}
                     <AgentTrace
-                      tools={msg.tools}
+                      tools={toolsWithLive(msg.tools, $activityLogProp, isLast && traceStatus !== 'idle')}
                       status={traceStatus}
                       label={traceStatus === 'idle' ? null : indicatorLabel}
                     />
@@ -306,9 +335,10 @@
           <div
             class="mb-2 flex items-center gap-2 rounded-md border border-warning/50 bg-warning/10 px-3 py-2 text-xs"
           >
-            <RefreshCwIcon class="size-3 shrink-0" aria-hidden="true" />
+            <RefreshCwIcon class="size-3 shrink-0 animate-spin text-warning" aria-hidden="true" />
             <span class="text-warning-foreground flex-1"
-              >Agent connection lost. The task may still be running.</span
+              >Connection dropped — the task is still running and will catch up here automatically.
+              Reconnect to refresh now.</span
             >
             <Button size="xs" variant="outline" class="h-6 text-[11px]" onclick={onReconnect}
               >Reconnect</Button