fix(cli): keep typing responsive by not blocking the keystroke loop

The interactive CLI input box runs its completer with
`complete_while_typing=True`, so `SlashCommandCompleter.get_completions`
is invoked on *every* keystroke. That completer does blocking I/O:
fuzzy `@`-file indexing shells out to `rg`/`fd` (up to a 2s timeout) and
file-path completion calls `os.listdir` + `stat`. Because the completer
was passed inline (never wrapped in `ThreadedCompleter`), all of this ran
synchronously on the prompt_toolkit event loop, stalling the render after
each key — very noticeable on WSL2 and other slow-filesystem setups
("typing in the prompt box being very latent").

Two fixes:

- Wrap the input completer in `ThreadedCompleter` so completion work runs
  off the UI event loop and never blocks rendering between keystrokes.
- Stop treating URLs as file paths in `_extract_path_word`: a token like
  `https://example.com/x` contains `/`, so it triggered `os.listdir` on
  every keystroke while typing/pasting a link (listing a bogus `https:`
  dir) for a completion that can never be useful. Skip any token with a
  `://` scheme separator.

hermes_cli/commands.py

@@ -1291,6 +1291,12 @@ class SlashCommandCompleter(Completer):
         word = text[i + 1:]
         if not word:
             return None
+        # URLs contain "/" but are not local paths. Treating them as paths fires
+        # os.listdir on every keystroke while typing/pasting a link (e.g. an
+        # https:// URL becomes a listdir of "https:") — pure latency, never a
+        # useful completion. Skip any token with a scheme separator.
+        if "://" in word:
+            return None
         # Only trigger path completion for path-like tokens
         if word.startswith(("./", "../", "~/", "/")) or "/" in word:
             return word