chore: drop tool-name markers from source comments

Seventeen comments opened with a tag naming the tool that wrote them.
The tag goes and each comment keeps its reasoning, now starting as a
plain sentence. None of the reasoning changes.

The AGENTS.md note in .gitignore drops the story of how the file got
into the tree and keeps the one fact a reader needs: its advice to run
go fmt is destructive on this CRLF working tree.

Comments only; no code, build or test changes.

cmd/felis/nano.go

@@ -37,7 +37,7 @@ import (
 
 // nanoStubRepo satisfies api.Repo but implements only the one method handleHasJoined calls.
 // The reclaim username blacklist is a felis-api/DB concern; a nano host has no Postgres, so
-// nothing is barred here. ponytail: a real blacklist would need the very DB nano exists to
+// nothing is barred here. A real blacklist would need the very DB nano exists to
 // avoid — YAGNI until a nano host grows a reclaim store.
 type nanoStubRepo struct{ api.Repo }