build: point differential-dataflow patch at the fork PR branch

Repoint the [patch.crates-io] entry for differential-dataflow and
differential-dogs3 from the local sibling checkout to the fork branch
(antiguru/differential-dataflow, the Arc-batches PR). Prototype plumbing until
that lands upstream and a released version carries arc_blanket_impls.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FwFQJa3HSy8oGJZ3X9uGZx

Author: claude

Cargo.lock

@@ -644,11 +644,11 @@ debug-assertions = true
 # merged), after which point it becomes impossible to build that historical
 # version of Materialize.
 [patch.crates-io]
-# Arc'd batches for cross-thread arrangement sharing, from a sibling checkout of
-# the fork. Prototype plumbing: repoint at a git rev (or drop the patch) once an
-# upstream differential-dataflow release carries the `arc_blanket_impls` module.
-differential-dataflow = { path = "../differential-dataflow/differential-dataflow" }
-differential-dogs3 = { path = "../differential-dataflow/dogsdogsdogs" }
+# Arc'd batches for cross-thread arrangement sharing, from the branch behind
+# TimelyDataflow/differential-dataflow#807. Prototype plumbing: repoint at a
+# released version (and drop the patch) once that PR lands upstream.
+differential-dataflow = { git = "https://github.com/antiguru/differential-dataflow", branch = "claude/spines-differential-arc-j93mho" }
+differential-dogs3 = { git = "https://github.com/antiguru/differential-dataflow", branch = "claude/spines-differential-arc-j93mho" }
 
 # Waiting on https://github.com/sfackler/rust-postgres/pull/752.
 postgres = { git = "https://github.com/MaterializeInc/rust-postgres" }