refactor(desktop): slash block-list derives from the Python command registry; only 5 TS-only names stay hand-typed

34 of the 46 `NO_DESKTOP_SURFACE` rows in desktop-slash-commands.ts were a
byte-for-byte copy of `desktop=` on the matching CommandDef in
hermes_cli/commands.py (7 more were aliases of those rows). The live
`commands.catalog` already carries that metadata; the static list was the
offline fallback and would silently drift on the next registry edit.

Now `hermes_cli/commands.py::desktop_surface_registry()` is the one author
of `/name -> desktop` (aliases included). `scripts/dump_desktop_slash_registry.py`
writes it to apps/desktop/src/lib/desktop-slash-registry.json, which the
desktop imports as its offline fallback (`registryUnavailableSpecs`). Five
names the Python registry has never heard of stay in an explicit
`TS_ONLY_NO_DESKTOP_SURFACE` with the reason WHY: `/density /details /logs
/mouse` are Ink-process-local display toggles (handled in
ui-tui/src/app/slash/commands/core.ts; advertised via `_TUI_EXTRA`), and
`/pets` is the plural typo of the desktop's own `/pet` action. `/switch`
was never a block-list row (it is a `/resume` alias) — not a finding.

Cross-language contract: tests/hermes_cli/test_desktop_slash_registry.py
asserts the committed JSON == desktop_surface_registry() and that every
alias carries its canonical value; desktop-slash-commands.test.ts asserts
every dumped row is unavailable/unsuggested offline with the dumped reason
and that the TS-only set is disjoint from the dump. Both sides fail on
drift (sabotage: flipping one `desktop=` in commands.py -> Python test
"stale"; adding `/clear` to the TS-only list -> vitest disjointness fails;
dropping `registryUnavailableSpecs()` -> 4 existing vitest cases fail).

Behavior change: none for users. `/model` (`desktop="hidden"`) keeps its
local picker spec; `hidden` is a popover flag read from the live catalog.

Sites: apps/desktop/src/lib/desktop-slash-commands.ts::NO_DESKTOP_SURFACE
(46 rows) -> hermes_cli/commands.py::desktop_surface_registry (41 rows via
the dump) + TS_ONLY_NO_DESKTOP_SURFACE (5 rows). apps/desktop/src/AGENTS.md
updated.

scripts/dump_desktop_slash_registry.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+"""Regenerate apps/desktop/src/lib/desktop-slash-registry.json from COMMAND_REGISTRY.
+
+Run after changing any ``desktop=`` value or alias in ``hermes_cli/commands.py``;
+``tests/hermes_cli/test_commands.py`` fails until the committed copy matches.
+"""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent.parent
+OUT = ROOT / "apps" / "desktop" / "src" / "lib" / "desktop-slash-registry.json"
+
+
+def render() -> str:
+    sys.path.insert(0, str(ROOT))
+    from hermes_cli.commands import desktop_surface_registry
+
+    return json.dumps(desktop_surface_registry(), indent=2, sort_keys=True) + "\n"
+
+
+if __name__ == "__main__":
+    OUT.write_text(render(), encoding="utf-8")
+    print(f"wrote {OUT.relative_to(ROOT)}")