A docstring that points at a section title must point at one the module carries

What happens today

scripts/feishu-gate.py has a module docstring organised in titled sections, each title
underlined by a row of dashes. The section about what happens to an approval is titled
Spent before it is sent.

The OutcomeUnknown class's docstring (same file) tells the reader where to look:

It is its own class because the caller's next move differs from the one a plain Refusal
allows — see "One approval, one message, spent before it is sent" in this module's docstring.

No section carries that title, and none ever has. A reader who follows the citation searches the
module docstring for a heading that is not there, and the sentence it was sent for — the reason the
class exists — is the one thing the pointer was supposed to save them from re-deriving.

The same file has a second citation of the same shape that does resolve
(See "Spent before it is sent" in the module docstring), and scripts/check-doc-count.py has a
third (See "Scope" in the module docstring, where the section title is Scope, stated with its measurement). So the convention is real and mostly honoured; the defect is that nothing checks it,
which is why one site drifted.

What is expected

A citation of the form see "<title>" in [this ]module's docstring names something the reader can
find. Where the citation does not resolve, the two are reconciled — the citation follows the
section's real title, or the section is retitled — and the choice is stated in the change.

What the fix must satisfy

• Every citation of that shape resolves against a section title the module's own docstring carries.
  None is left pointing at a title that does not exist.
• The rule is mechanised, not restated in prose: a guard reads the citations out of the source
  and checks them against the module docstring's own titles, so the next drift is caught rather than
  discovered.
• The subject is discovered, not listed: the titles are the lines a docstring itself underlines,
  and the citations are found by pattern. A hand-written list of files or titles admits every
  position it omits, and the class this defect belongs to is not confined to the files that carry it
  today.
• The guard is shown to fail on the defect as it exists now and to pass once it is corrected —
  an arm that reports the pre-change tree green has measured nothing.
• A citation that matches an underlined title only in part (Scope against Scope, stated with its measurement) counts as resolving: the reader is being sent to a section, and a section found by
  its opening words is found. A citation that matches no title at all is the defect.