* Wire manifest.AfterDephantomize into the phantom fill path

AfterDephantomize was a faithful, tested port of Fossil's after_dephantomize (content.c:389-456) that nothing in production ever called — it crosslinked correctly in isolation but sat disconnected from the real receive path.

storeResolvedContent fills a phantom row in place when the full content for a previously-unknown UUID arrives (matching canonical's content_put_ex filling a phantom at content.c:626), but stopped short of crosslinking it or any delta children waiting on it. Return the filled rid from storeResolvedContent and call AfterDephantomize on it from storeReceivedFile once the fill transaction has committed — outside the transaction, since AfterDephantomize opens its own connection via repo.Repo.DB() and calling it from inside the tx's closure would contend with the still-open write lock.

Added an end-to-end regression test that delivers a checkin manifest as a delta against a base that hasn't arrived yet, then delivers the base, and asserts the manifest is crosslinked (its event row exists) immediately — with no explicit call to manifest.Crosslink anywhere in the test. This proves AfterDephantomize fires on the real fill path, not only under its own unit tests.

* Log crosslink failures during AfterDephantomize instead of swallowing them

A crosslink error while filling a phantom blob (or one of its orphan/delta dependents) previously vanished silently, leaving storeReceivedFile report success with the artifact filled but un-crosslinked. Surface it via slog.Warn so real corruption on the fill path is at least visible, matching the non-blocking nit from review. check-in: 94919ca357 user: [email protected] tags: trunk