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>

tests/test_hermes_state.py

@@ -3509,3 +3509,43 @@ class TestApplyWalProbe:
         assert any("journal_mode=WAL" in sql for sql in conn.executed), (
             "set-pragma must fire when probe returns 'delete'"
         )
+
+
+class TestSessionArchive:
+    """Soft-archiving hides a session from default listings without deleting it."""
+
+    def _seed(self, db, sid, *, archived=False):
+        db.create_session(session_id=sid, source="cli")
+        db.append_message(session_id=sid, role="user", content=f"hello from {sid}")
+        if archived:
+            db.set_session_archived(sid, True)
+
+    def test_set_session_archived_roundtrip(self, db):
+        self._seed(db, "s1")
+        assert db.set_session_archived("s1", True) is True
+        assert db.get_session("s1")["archived"] == 1
+        assert db.set_session_archived("s1", False) is True
+        assert db.get_session("s1")["archived"] == 0
+
+    def test_set_session_archived_missing_row(self, db):
+        assert db.set_session_archived("nope", True) is False
+
+    def test_archived_excluded_by_default(self, db):
+        self._seed(db, "live")
+        self._seed(db, "hidden", archived=True)
+
+        ids = [s["id"] for s in db.list_sessions_rich()]
+        assert ids == ["live"]
+        assert db.session_count() == 1
+
+    def test_archived_only_and_include(self, db):
+        self._seed(db, "live")
+        self._seed(db, "hidden", archived=True)
+
+        only = [s["id"] for s in db.list_sessions_rich(archived_only=True)]
+        assert only == ["hidden"]
+        assert db.session_count(archived_only=True) == 1
+
+        both = {s["id"] for s in db.list_sessions_rich(include_archived=True)}
+        assert both == {"live", "hidden"}
+        assert db.session_count(include_archived=True) == 2