docs: the receipt carry follows a stamp on the branch's own rows (GST-980)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/ship-policy.md

@@ -1359,6 +1359,7 @@ receipt when the base moves:
 | a rebase or force-push onto a tree the receipt covers, product diff against the new base unchanged | carries (`carry.ancestry: rewritten`) |
 | any other rebase or force-push | a fresh /ship (`RECEIPT_CARRY_TREE_MISMATCH`) |
 | a stacked PR whose parent landed (squash or merge), retargeted to the base with the base merged in, HEAD's product diff exactly the one reviewed against the parent branch | carries (reason `stack parent <branch> landed`) |
+| a stamp on the branch's own rows in a stamp file the branch also changed as product: every changed line at a branch-added position, the file's mode unchanged, the base not touching it, the rest of the product diff unchanged | carries (reason `a stamp on the branch's own rows (<file>)`) |
 
 **Stacked PRs (#3570).** A child PR's receipt is written against its parent
 branch, so its `base` names that branch and its `product_patch_id` is the

docs/troubleshooting.md

@@ -5860,8 +5860,10 @@ retargeted stacked PR the parent branch and the base.
 conflict-only base merge, a test-only change, release metadata, a registered
 output the pregate's regen check proved, a rebase onto a covered tree with
 the recorded product diff, a stacked PR's retarget once its parent fully
-landed on the base, or base context next to unchanged hunks after a clean
-scoped review ([`RECEIPT_CARRY_SCOPED_REVIEW`](#receipt-carry-scoped-review)), which the
+landed on the base, a stamp on the branch's own rows in a stamp file it also
+changed as product (every changed line at a branch-added position, the mode
+unchanged, the base not touching the file), or base context next to unchanged
+hunks after a clean scoped review ([`RECEIPT_CARRY_SCOPED_REVIEW`](#receipt-carry-scoped-review)), which the
 `carry` object in the carried receipt records with the product patch-id and
 the range-diff evidence ([unattended.md](unattended.md#the-terminal-line)).