[NullVoxPopuli-ai-agent]

Merge #21726 first. This PR sits on top of it. Review only the last commit, 82f2441334.

With EMBER_DROP_CLASSIC_FEATURES=true, @ember/object/computed exports undefined for the 15 macros of the deprecate-computed-macros deprecation (#21688):

alias, and, bool, deprecatingAlias, equal, gt, gte, lt, lte, match, not, oneWay, or, readOnly, reads

export const readOnly = (
  import.meta.env?.EMBER_DROP_CLASSIC_FEATURES ? undefined : macros.readOnly
) as typeof macros.readOnly;

• The macros do not throw. They are not exported.
• A cast keeps the published types without | undefined.
• empty, notEmpty, none and the array macros stay, because other deprecations cover them.

Tests

• The tests of these macros skip when the flag is set, as they skip when the deprecation is removed. This includes 13 tests in macro_decorators_test.js that check the "used without parameters" assertion.
• length_test.js: one test used a deprecated macro, but did not skip when the deprecation is removed. It skips now.
• New packages/@ember/object/tests/computed/drop_classic_features_test.js checks that the 15 exports are undefined. It registers only with the flag.

Checks

Mode	Result
Default	9234 tests, 0 failures
ALL_DEPRECATIONS_ENABLED=true	9234 tests, 0 failures
OVERRIDE_DEPRECATION_VERSION=15.0.0	8257 tests, 0 failures
Production build	9071 tests, 0 failures
EMBER_DROP_CLASSIC_FEATURES=true	9235 tests, 0 failures

The type checks of the internals and of the published types (with and without stable decorators), eslint, prettier and the docs check pass.

🤖 Generated with Claude Code