v2: converting destroys, so extract first

v1 made the cart untracked and did not say what that does to conversion. Every
earlier version left the dailies in git, so "gone" was only ever true of the tree;
now it is true absolutely, and the agreement was silent.

Filed by loom-cli as first adopter, from three rounds: two rules now both push
toward loss — act as if the shelf is discarded daily, and the cart is not
committed — and neither said what has to be written down first. They staged a
write-ahead log as they went and noted they would not have thought of it
unsuggested, which is the whole argument for stating it here.

Names what must be extracted: every prompt answer, since an answer lands in a
notes file which dies at dissolve and an untracked cart has no history to fall
back on; every surviving write-ahead entry; and every fallback that quietly became
the decision. And the practice that makes it cheap — stage as you go, so
conversion is a move rather than a rewrite at the moment you have least appetite
for one.

This is a defect introduced this afternoon and repaired the same day, on a report
from the adopter who hit it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -64,3 +64,17 @@ bearing for weeks before it was written down here.*
 **The durable record must outlive the cart**, and therefore cannot be inside it.
 *Implied by "durable" and never stated, so an adopter could have cast it to a path
 in `.loom/cart/` and this document would not have told them otherwise.*
+
+## `v2` — 2026-09-07
+
+**One addition, and it repairs `v1` on the day it landed.**
+
+**Converting destroys.** *`v1` made the cart untracked without saying what that
+does to conversion — **every earlier version left the dailies in git**, so "gone"
+had only ever been true of the working tree.* **Now it is true absolutely**, and
+the agreement did not say so.
+
+*Filed by `loom-cli` as its first adopter, from three rounds: **"two rules now both
+push toward loss, and neither says what has to be written down first."*** *They
+staged a write-ahead log as they went and noted they would not have thought of it
+unsuggested.*