Fill all 568 missing translation keys in en_GB.json (765→1357 lines):
- 97 --help description keys (collect, ci, docs, dev, php, pkg, sdk, vm)
- 471 runtime keys (labels, errors, hints, progress, status messages)
- Add common.flag.follow, common.flag.tag, common.prompt.abort
Add completeness_test.go that scans all T() calls in source code and
verifies every cmd.*/common.* key exists using ModeStrict (panics on
missing). Catches translation gaps at test time instead of showing raw
keys in the CLI.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
