* gptel.el (gptel--convert-markdown->org,
gptel--stream-convert-markdown->org, gptel-set-topic): Move code
for transforming responses and setting the GPTEL_TOPIC property to
gptel-org. Add declarations for the byte-compiler.
* gptel-org.el (gptel-org-branching-context, gptel-org-set-topic,
gptel-org--restore-state, gptel--convert-markdown->org,
gptel--stream-convert-markdown->org): Add `gptel-org-set-topic` to
set the topic per heading in Org buffers. Fix typo in
gptel-org--restore-state. Add declarations for
the byte-compiler and page markers for the reader.