rename: braindump → coopertron (Coopertron 5000)

The tool names the whole experiment, not just this script, so it gets a
name with some personality. Repo, directory and command are `coopertron`;
"Coopertron 5000" is the display name in the README and the report title.
The activity the form captures is still a braindump.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -1,6 +1,7 @@
-# braindump
+# Coopertron 5000
 
-Anonymous braindump form + LLM synthesis for Inference Cooperative meetings.
+A benevolent robot that reads the co-op's anonymous pre-meeting braindump and
+tells the members what they said. Built for Inference Cooperative meetings.
 Members answer a short form before a meeting (ideas, wants, needs, goals,
 dissent). This script turns the export into a review document the group reads
 together: where energy is concentrated, what is unusual, where people disagree.
@@ -129,3 +130,6 @@ lives on CryptPad for now; a small co-op-hosted app (anonymous form + a
 synthesize button, same pipeline) is a possible next step if the output is
 useful. Discussion and ideas: open an issue here or on
 [co-op/support](https://git.inference.coop/co-op/support/issues).
+
+Why the name: it is a small experiment with a big-robot name, on purpose. The
+repo and command are `coopertron`; the 5000 lives in prose only.