Answer A-93: a branch's take-in computes its revision directly; the trunk stays main

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

03-DESIGN/01-to-be/47-milestones/G-20-lead-answers.md

@@ -350,7 +350,7 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-90** (§13, §14, §291, ADR 0666 §6, A-85; principle 7) A non-first branch's revision is made by the same take-in as
   the trunk's, taken per watched branch: `sourceFollow` takes `source.<branch>` for every watched branch, and the
   source path (`ApplySource`, the catch-up, the heads' take-in) runs with the branch as its argument, writing that
-  branch's revision; the trunk is each registration's first branch, not a constant.
+  branch's revision (corrected by A-93).
 - **A-91** (§26, §37, §700, Q-RN8; principle 7) The router's record value carries its `warrant` as §700 says: the
   operator-channel contract's `AsksByAskerIDValue` gains the field. A step the module's policy does not name is no step
   of its pipeline, so `Status` has no open question for it. The runner places a pipeline's steps when it starts it and
@@ -358,3 +358,9 @@ names the principle that settles it, and is cited as "design 47 G A-n".
 - **A-92** (§560, A-77, §627; principle 7, and who may do what is no question) The node-engine's bound keys live in a new
   state `bounds` of the seat `node-engine`'s definition, declared in its old section as a foundation part's states are
   (§627), key `<what>.<id>` with its own time to live; the node-engine's account holds it as it holds its other states.
+- **A-93** (§13, §14, §291, ADR 0666 §6, A-85, A-90; principle 7; corrects A-90's trunk) A non-first branch's take-in
+  is a pure computation from that branch's merged messages straight into its revision (`KeepBranchEntries`): each
+  module's fingerprint, inputs and graph node at the branch's heads, computed as the trunk's are, with no modules view
+  or bucket of its own; the trunk's `modules`, `manifests` and graph stay the trunk's alone. The trunk stays the
+  mesh-wide branch `main` (ADR 0666's default watched branch), named once in the indexer; a registration's own first
+  branch decides only which of its branches it delivers from.