PR #11 merged: feat(app): human-readable rollpack-<timestamp> pack names

Names packs rollpack-YYYY-MM-DD-HH-MM-SS at creation (local wall-clock via chrono) instead of the opaque rec-<epoch_ms>.

The epoch was never load-bearing — traced it: only a unique id + lexical(=chronological) sort key, and it was shown raw in the UI. Nothing parsed it back to a date.

• lib.rs name gen uses chrono::Local + a -2/-3 same-second collision guard
• list_packs gate accepts rollpack- and legacy rec- (existing packs still list)
• sort unchanged (b.id.cmp(&a.id) — ISO order is lexical order)
• gitignore the untracked local scripts/roll-push.sh sandbox-sync watcher

Compiles clean under RUSTFLAGS="-D warnings".