fix(editor): fall back to $EDITOR and defaults when $VISUAL is unset

[dbactual]

Problem

getSystemEditor() in internal/editor/editor.go returned an empty string immediately when $VISUAL was unset, skipping the $EDITOR fallback and the vi/emacs default. This broke edit-and-execute-command (Ctrl-X Ctrl-E) with:

Editor error: failed to start editor: exec: no command

This is the common case, since most users set only $EDITOR.

Fix

Check each fallback in order (per the doc comments on editAndExecuteCommand in emacs.go and editAndExecute in vim.go) and return the first non-empty value; fall back to vi (or emacs when emacsDefault) only when both env vars are unset.

Testing

• go build ./... passes (the package has no tests)
• Manually verified: with VISUAL unset and EDITOR=vim, Ctrl-X Ctrl-E now opens vim

[codecov]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 39.82%. Comparing base (196a349) to head (f2d6a09).

Files with missing lines	Patch %	Lines
internal/editor/editor.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #122   +/-   ##
=======================================
  Coverage   39.82%   39.82%           
=======================================
  Files          60       60           
  Lines        9595     9594    -1     
=======================================
  Hits         3821     3821           
+ Misses       5680     5679    -1     
  Partials       94       94           

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[maxlandon]

Thanks for the fix !