feat(web+nomos): fix chat streaming reactivity, unified activity timeline, tool cards in chat

- fix(web): Svelte 5 identity-based reactivity broke text_delta streaming —
  immutable message objects in all three chat handlers so text streams live
- feat(web): streaming cursor + inline status indicator merged into message flow
- feat(web): expandable inline tool call cards in chat thread
- feat(web): merge Plan + Event log into one backbone Activity timeline —
  filled status nodes, branch stubs, auto-scroll follow mode, per-session
  activityLog, compact for the rail
- fix(nomos): add X-Accel-Buffering:no to /chat SSE (proxy buffering)
- fix(nomos): plan step auto-close SQL param bug (store.go)
- polish: timestamps, role labels, code copy button, table overflow, min
  window size, delete AgentIndicator/ActivityTimeline dead code

web/src/lib/components/SessionChatWindow.svelte

@@ -1,13 +1,12 @@
 <script lang="ts">
-  // Floating-window content for a task/session — the per-window counterpart
-  // to the main Chat page (thread + rail), fully self-contained per
+  // Floating-window content for a task/session — self-contained per
   // sessionId via chat.ts's chatFor()/loadSessionChat()/sendSessionMessage()
   // and workspace.ts's workspaceFor()/startSessionWorkspace(), so several of
-  // these can be open (and independently live) at once without the "which
-  // one's on screen" guarding the main page's singleton stores need.
+  // these can be open (and independently live) at once.
   import { onDestroy, onMount } from 'svelte'
   import { Pane, Splitpanes } from 'svelte-splitpanes'
   import { chatFor, loadSessionChat, sendSessionMessage, cancelSessionStream, stopSessionPolling, dismissError, chatErrors } from '$lib/stores/chat'
+  import { activityLogFor } from '$lib/stores/activity'
   import ChatThread from '$lib/components/ChatThread.svelte'
   import TaskContextPanel from '$lib/components/TaskContextPanel.svelte'
 
@@ -16,12 +15,17 @@
   // Svelte's `$store` auto-subscription only works on a plain identifier
   // bound directly to a store, not a member expression — chatFor() returns
   // an object of stores, so pull each one out into its own identifier here.
+  // sessionId is a stable prop (one per window mount, never changes), so
+  // capturing it at init is safe and intended.
+  // eslint-disable-next-line svelte/valid-compile
   const chat = chatFor(sessionId)
   const chatMessages = chat.messages
   const chatStreaming = chat.streaming
   const chatConnectionState = chat.connectionState
   const chatError = chat.error
   const chatNotFound = chat.notFound
+  // eslint-disable-next-line svelte/valid-compile
+  const sessionActivityLog = activityLogFor(sessionId)
   let loading = $state(true)
 
   onMount(async () => {
@@ -53,6 +57,7 @@
           connectionState={$chatConnectionState}
           error={$chatError}
           chatErrors={$chatErrors}
+          activityLog={sessionActivityLog}
           onSend={(text) => sendSessionMessage(sessionId, text)}
           onCancel={() => cancelSessionStream(sessionId)}
           onReconnect={() => loadSessionChat(sessionId)}