v15.4.0-canary.18

Core Changes

• remove draft.isEnabled setter from exotic draftMode wrappers: #77972
• Turbopack: limit compaction merging by size instead of count: #78669

Misc Changes

• Update authentication.mdx: #78738
• chore(CI): Use TEST_CONCURRENCY by default in run-tests.js: #78731
• Update test new tests for deploy mode: #78737
• Update Turbopack development test manifest: #78741

Credits

Huge thanks to @xyf7, @bgw, @ijjk, @lubieowoce, and @sokra for helping!