feat(desktop): session hygiene, archive, media streaming + connecting overlay (#37099)

* feat(desktop): session hygiene, archive, media streaming + connecting overlay

Address a batch of desktop feedback:

- Stop leaking empty "Untitled" sessions: the TUI gateway pre-created a DB
  row on every session.create (i.e. every launch/draft). Persist the row
  lazily on first prompt instead, and hide message-less rows in the sidebar.
- Archive/hide sessions: new `archived` column + set_session_archived, web
  API (`?archived=` + PATCH archived), Ctrl/⌘-click and a context-menu item
  in the sidebar, and an "Archived Chats" settings panel to restore/delete.
- Videos load via a streaming `hermes-media://` protocol instead of capped,
  in-memory data URLs (16 MB limit) — bypasses the cap and supports seeking.
- Background-process completions route to the session that launched them:
  the completion event now carries session_key and each poller only consumes
  its own.
- Sidebar: "Group by workspace" toggle is always visible; each workspace
  group gets a "+" to start a session in that directory; "New agent"/"Agents"
  relabeled to "New session"/"Sessions".
- New gateway connecting overlay (ascii decode → fade out) replacing the bare
  skeleton/"starting gateway" state.

* fix(desktop): bail connecting overlay on boot error

The shownRef latch kept the connecting overlay mounted behind
BootFailureOverlay after a hard boot failure. Return null on boot.error
so the failure recovery surface fully owns the screen.

* fix(desktop): address Copilot review

- /api/sessions: validate `archived` (400 on unknown) and return `archived`
  as a JSON boolean instead of SQLite's 0/1.
- PATCH /api/sessions/{id}: 400 (not a misleading 404) when the body has no
  updatable fields; stop conflating a no-op with "not found".
- hermes-media protocol: drop `bypassCSP` — streaming only needs
  secure/standard/stream/supportFetchAPI.
- Sidebar workspace header: split the toggle and the "+" into sibling buttons
  so we no longer nest interactive elements inside a <button>.

* fix(desktop): address Copilot re-review

- hermes-media protocol: restrict streaming to an audio/video extension
  allowlist (415 otherwise) so it can't be used to read arbitrary local files.
- Connecting overlay: use z-[1200] instead of the non-standard z-1200 utility.

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

apps/desktop/src/app/session/hooks/use-session-actions.ts

@@ -2,7 +2,7 @@ import type { MutableRefObject } from 'react'
 import { useCallback, useRef } from 'react'
 import type { NavigateFunction } from 'react-router-dom'
 
-import { deleteSession, getSessionMessages } from '@/hermes'
+import { deleteSession, getSessionMessages, setSessionArchived } from '@/hermes'
 import { type ChatMessage, chatMessageText, preserveLocalAssistantErrors, toChatMessages } from '@/lib/chat-messages'
 import { normalizePersonalityValue } from '@/lib/chat-runtime'
 import { embeddedImageUrls, textWithoutEmbeddedImages } from '@/lib/embedded-images'
@@ -751,7 +751,39 @@ export function useSessionActions({
     ]
   )
 
+  const archiveSession = useCallback(
+    async (storedSessionId: string) => {
+      clearNotifications()
+
+      const archived = $sessions.get().find(s => s.id === storedSessionId)
+      const wasSelected = selectedStoredSessionId === storedSessionId
+      const previousPinned = $pinnedSessionIds.get()
+
+      // Soft-hide: drop from the sidebar immediately, keep the data.
+      setSessions(prev => prev.filter(s => s.id !== storedSessionId))
+      $pinnedSessionIds.set(previousPinned.filter(id => id !== storedSessionId))
+
+      if (wasSelected) {
+        startFreshSessionDraft(true)
+      }
+
+      try {
+        await setSessionArchived(storedSessionId, true)
+        notify({ durationMs: 2_000, kind: 'success', message: 'Archived' })
+      } catch (err) {
+        if (archived) {
+          setSessions(prev => [archived, ...prev.filter(s => s.id !== storedSessionId)])
+        }
+
+        $pinnedSessionIds.set(previousPinned)
+        notifyError(err, 'Archive failed')
+      }
+    },
+    [selectedStoredSessionId, startFreshSessionDraft]
+  )
+
   return {
+    archiveSession,
     branchCurrentSession,
     closeSettings,
     createBackendSessionForSend,