Add Claude Code hooks, commands, and permissions

High priority:

- Auto-format on edit (.claude/hooks/format-elixir.sh): runs mix format
  synchronously after every Edit/Write on .ex, .exs, and .heex files.
  Ensures code is formatted before the next read or tool call.

- mix test permissions: added Bash(mix test) (bare) and Bash(mix test *)
  (with path/flags) to the allow list. Previously only Bash(mix test:*)
  was allowed, which didn't match common invocations.

- Slash commands: /precommit runs the full mix precommit pipeline and
  reports failures with fix suggestions. /oban-status queries Oban job
  state via Tidewave SQL, grouped by state and worker.

Medium priority:

- Chrome DevTools permissions: added 8 new tools (select_page,
  list_network_requests, get_network_request, list_console_messages,
  get_console_message, hover, press_key, wait_for) for debugging API
  traffic, JS hook errors, hover states, and keyboard navigation.

- Gettext extraction hook (.claude/hooks/gettext-extract.sh): runs
  mix gettext.extract --merge asynchronously after editing .heex files.
  Async because it's project-wide and doesn't need to block the next edit.

- Sobelow permission: added Bash(mix sobelow:*) to the allow list for
  independent security checks.

.claude/commands/precommit.md

@@ -0,0 +1 @@
+Run the full pre-commit check pipeline (`mix precommit`) and report the results. If any check fails, identify the specific failure and suggest a fix.