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/backup.go

@@ -116,7 +116,7 @@ func newBackupID() string {
 	var b [16]byte
 	if _, err := rand.Read(b[:]); err != nil {
 		// crypto/rand failure is fatal and unrecoverable; a time-based fallback would
-		// be a weaker ID for no benefit. ponytail: panic is the honest failure here.
+		// be a weaker ID for no benefit. A panic is the honest failure here.
 		panic("felis backup: crypto/rand: " + err.Error())
 	}
 	return "bk-" + hex.EncodeToString(b[:])

cmd/felis/initforwarding.go

@@ -26,7 +26,7 @@ const defaultForwardingDataDir = "/data"
 // volume of unknown ownership; 0666/0777 then let a non-root Paper rewrite the
 // same files on boot.
 //
-// ponytail: relies on the initContainer running as root to write into a volume of
+// This relies on the initContainer running as root to write into a volume of
 // unknown ownership; that is how the operator schedules it. If that ever changes,
 // give the server pod an fsGroup so the shared volume is group-writable instead.
 const (

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 }