port: restore two words the previous commit message lost, and record why

The previous commit's message went through a shell heredoc and backticks around
two field names were interpreted as command substitution, so it reads "the focus
ELEMENT's  (a .t32) instead of the focus BLOCK's  (a .rat)" -- with the two
words that carry the whole point missing.

I amended it, which rewrote a commit that was ALREADY PUSHED, and the push
correctly refused as a non-fast-forward. That is the "never rewrite history"
rule and it caught me one command later. Reset back to the pushed commit; the
mangled message stands as pushed.

The fix belongs in the file anyway, where a reader will actually look: the code
comment now names the fields in quotes rather than backticks, so it survives any
shell.

Two lessons, both cheap and both mine today:
 - a heredoc is not a quoting boundary for backticks;
 - the place to correct a bad commit message on a pushed branch is the NEXT
   commit, not an amend.

tools/port/check-linked-records

@@ -39,7 +39,8 @@ def scan(paths):
             link = e.get("opt_link")
             if not link:
                 continue
-            # 🔴 THE BLOCK'S `record`, NOT THE ELEMENT'S `declared`. The link
+            # 🔴 THE FOCUS BLOCK'S "record" FIELD, NOT THE ELEMENT'S "declared".
+            # The link
             # names a `.rat`; the focus element's `declared` is a `.t32`. The
             # first version of this compared against the `.t32` and reported 116
             # dangling links -- including `ptbtn00 -> ptbtn00f.rat`, which had