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/components/assistant-ui/markdown-text.tsx

@@ -19,9 +19,9 @@ import {
   filePathFromMediaPath,
   mediaExternalUrl,
   mediaKind,
-  mediaMime,
   mediaName,
-  mediaPathFromMarkdownHref
+  mediaPathFromMarkdownHref,
+  mediaStreamUrl
 } from '@/lib/media'
 import { previewTargetFromMarkdownHref } from '@/lib/preview-targets'
 import { cn } from '@/lib/utils'
@@ -40,24 +40,22 @@ import { cn } from '@/lib/utils'
 // LLM convention). The default false-setting only accepts `$$...$$`.
 const mathPlugin = createMemoizedMathPlugin({ singleDollarTextMath: true })
 
-async function typedBlobUrl(dataUrl: string, mime: string): Promise<string> {
-  const blob = await fetch(dataUrl).then(response => response.blob())
-
-  return URL.createObjectURL(new Blob([await blob.arrayBuffer()], { type: mime }))
-}
-
 async function mediaSrc(path: string): Promise<string> {
   if (/^(?:https?|data):/i.test(path)) {
     return path
   }
 
+  // Stream audio/video through the custom protocol: data URLs are capped and
+  // load the whole file into memory, which broke playback for larger videos.
+  if (window.hermesDesktop && ['audio', 'video'].includes(mediaKind(path))) {
+    return mediaStreamUrl(path)
+  }
+
   if (!window.hermesDesktop?.readFileDataUrl) {
     return mediaExternalUrl(path)
   }
 
-  const dataUrl = await window.hermesDesktop.readFileDataUrl(filePathFromMediaPath(path))
-
-  return ['audio', 'video'].includes(mediaKind(path)) ? typedBlobUrl(dataUrl, mediaMime(path)) : dataUrl
+  return window.hermesDesktop.readFileDataUrl(filePathFromMediaPath(path))
 }
 
 function OpenMediaButton({ kind, path }: { kind: 'audio' | 'video'; path: string }) {
@@ -278,10 +276,7 @@ const MarkdownTextImpl = () => {
   // render, which churns Streamdown's outer memo + propagates new prop
   // identities into every Block. The plugin set really only varies on
   // `isStreaming`, so memoize on that.
-  const plugins = useMemo(
-    () => (isStreaming ? { math: mathPlugin } : { math: mathPlugin, code }),
-    [isStreaming]
-  )
+  const plugins = useMemo(() => (isStreaming ? { math: mathPlugin } : { math: mathPlugin, code }), [isStreaming])
 
   const components = useMemo(
     () =>