§13.6 + §10.1/§10.2: walking distinguished heads and fork detection

[OR13]

Not implemented. No peer: grep -ril 'DistinguishedRequest\|DistinguishedHead' upstream/katie/ returns nothing, so this lands as implemented-unverified however well it is written.

To implement:

• DistinguishedRequest / DistinguishedResponse (§13.6) and DistinguishedHead (§10.2) wire types. Note the bound was corrected to heads<0..2^8-1> on 2026-07-28.
• §12.3.7's proof contents, ordered by §10.1's walk.
• §10.2's prefix-or-suffix check between the authenticated and partition-resistant channels. The draft ships example Python code for it, which is a real oracle — transcribe it as a reference the way Appendix A's log2/level already are in ibst.rs.

§10.1's walk is already implemented in kt-tree::distinguished and is one of the two implemented-unverified rows. The most that can be anchored against katie is its two ends: the walk must start at algorithms.RightmostDistinguished and, under "recent = all", visit algorithms.PreviousRightmost second. Worth doing as a partial anchor; it does not make the row verified.

Also from §10.1, unimplemented: "An application's definition of 'recent' SHOULD NOT generally be expected to include more than ten distinguished log entries" (added 2026-07-28).