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.

internal/fileedit/exec.go

@@ -220,7 +220,7 @@ func list(r *os.Root, path string) Result {
 // denied; a write is left alone because writing the file leaks nothing and is
 // equally futile.
 //
-// ponytail: an exact match on one cleaned path, not a pattern. This is the whole
+// An exact match on one cleaned path, not a pattern. This is the whole
 // known exposure — grep FELIS_FORWARDING_SECRET across deploy/ — and if another
 // image ever persists a platform secret into the mount, add its path here rather
 // than inventing a matcher.