bv0: open @file references from the 'o' key in $EDITOR

The 'o' key now opens an @path/to/file.txt reference in $EDITOR in the
foreground when the task carries no URL. URLs keep precedence so the
original open-URL behavior is unchanged when both are present.

- Add fileRefRegex plus extractFileRef/findTaskFileRef/resolveFileRefPath
  helpers: scan description then annotations, expand a leading ~, and
  anchor on (^|\s) so email @host parts are not treated as references.
- openFileInEditorCmd mirrors launchDescriptionEditorCmd, using
  tea.ExecProcess to suspend the TUI, run the editor on the real
  terminal, and restore the TUI on exit.
- Refactor handleOpenURL into small helpers to stay under the size limit.
- Add fileref_test.go covering parsing, ~ expansion, annotation fallback,
  and URL precedence.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions