Fixes https://github.com/twentyhq/twenty/issues/21094
Conditional availability variables (`objectMetadataItem`,
`numberOfSelectedRecords`, `objectPermissions`, operators like
`everyEquals`/`none`, etc.) are compile-time-only constructs used in
`conditionalAvailabilityExpression`. They were previously exported from
`twenty-sdk/front-component`, which let developers mistakenly import
them into runtime component code where they have no value.
- Move conditional availability variables from
`twenty-sdk/front-component` to `twenty-sdk/define`.
- Add a build-time manifest validation
(validate-conditional-availability-usage) that fails the build if these
variables are imported/used outside of
`conditionalAvailabilityExpression`.
- Update the github-connector example app to register commands via
dedicated *.command-menu-item.ts files instead of inline command config
in front components.
- Update docs (all locales) and test mocks to reflect the new import
paths.
Add a note to the command menu items docs explaining that
RECORD_SELECTION already guarantees a non-empty selection, so
numberOfSelectedRecords > 0 is redundant in
conditionalAvailabilityExpression.
