merge(ready): reconcile preserved parent traversal work with current main

Join the June salvage history after verifying its useful implementation
is already canonical. All added ready-command lines and storage BFS,
visited-set, parent-member resolution and plain-ID filtering lines are
present in current source after whitespace normalization. The only
textual exception is the expanded collections import; the required
VecDeque remains imported. Main c744dae1 integrated the behavior and
later ba8d0f26 strengthened filtering for SQL parameter limits.

Six of eleven branch paths have exact blobs in main history, including
the tracker snapshot. Keep newer dependency and action pins. Do not
replay historical removals from sync recovery invariants or performance
notes: those removals erase qualifications that import/doctor checks
were not executed and replace their recorded failures with unsupported
success values. The retained current evidence remains more accurate.

Validation: reviewed the complete remaining source and evidence deltas,
compared added source lines with main, and audited branch blobs against
main history. This merge preserves the exact current tree and the old
history without manufacturing a test pass or editing implementation.