Make reads eviction-safe: download offloaded iCloud files instead of losing them

Wires the previously-dead ensureDownloaded into every read (it now polls,
bounded 30s, instead of fire-and-forget) and fixes the deeper hole: the
directory listing skipped hidden files, so evicted records — whose only local
trace is a hidden .<name>.json.icloud placeholder — never appeared in
reconcile at all and their cache entities were pruned as deleted.

Also: reconcile no longer prunes entities whose file failed to read this pass
(an eviction-download timeout is not a deletion); tombstone IDs come from stub
filenames so an evicted stub still vetoes resurrection; the stale-file stub
check is placeholder-aware; read failures log loudly instead of try?-skipping.

Verified with a harness compiling the real ICloudFileManager against a local
temp directory (placeholder mapping, dedup, tombstone derivation, soft-delete
round trip). Real eviction/download behavior needs a device pass.

Claude-Session: https://claude.ai/code/session_01SY5jsAUf4qoPxSvv8xAqXS

CHANGELOG.md

@@ -1,3 +1,7 @@
+**July 2026**
+
+Fixed workouts and splits vanishing from the app when iPhone storage ran low: when iOS offloads their files to iCloud to free up space, Workouts now downloads them back automatically instead of treating them as gone.
+
 **June 2026**
 
 Starting a new workout while another is still going now asks whether to end the current one first or run both in parallel.