Merge PR #640: fleetd #639 — redact()'s comment claimed more than the code does

Comment text only, no behaviour change. Corrects the paragraph added in d7f94ca so it no longer
claims the continuation masking holds for any masked key "present or future". It holds only while
the masked key's own line is inside the printed hunk; diff -u's three lines of context routinely
leave it out, and a blank line inside a block scalar drops the anchor too.

Verified: suite green in a clean copy of the edited tree (16 criteria + 3 extras, exit 0), bash -n
clean, and a control on the edit itself (old claim gone, #639 reference present). Evidence in #639.

scripts/config-edit.sh

@@ -159,7 +159,13 @@ done
 # The fix is structural, not another name to match: once a key line is masked, every following
 # line indented STRICTLY DEEPER than that key is masked too, by indentation alone, until the
 # indentation returns to the key's own level or shallower. This needs no knowledge of the key's
-# name and so protects a block scalar under any masked key, present or future.
+# name, so it covers a block scalar under any masked key — but ONLY while that key's own line is
+# itself inside the hunk being printed. `diff -u` prints just three lines of context, so a block
+# scalar's body often reaches this function with its key line left out; there is then nothing to
+# anchor to, `masked` is never set, and the body prints in full. A blank line inside a block
+# scalar loses the anchor the same way, because a blank diff line measures as indent 0. Both are
+# measured and filed as fleetd #639 — do not read this paragraph as a guarantee that a masked
+# key's value can never be printed.
 #
 # `redact` is always fed `diff -u` output, and every line of a unified diff starts with exactly
 # one of ' ', '+', '-' (the three body markers; '@'/'-'/'+' for the three header-line kinds too).