docs: rename CLAUDE.md to AGENTS.md and rebrand provider-agnostic

Delete CLAUDE.md in favor of AGENTS.md as the orientation doc, rebrand
the project from Codex-bottle to provider-agnostic bot-bottle, and
repoint every CLAUDE.md reference across PRDs, research notes, the
implementer agent example, and the yaml_subset comment.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/research/network-egress-guard.md

@@ -734,7 +734,7 @@ Key PRD scope for this work:
 - Add a dnsmasq configuration step: install dnsmasq in the Dockerfile, configure
   it to serve only allowlisted names, and set `--dns 127.0.0.1` in `docker run`.
 - Block outbound UDP port 53 to non-dnsmasq resolvers in the iptables rules.
-- Document the `--cap-add` changes in `CLAUDE.md` under security.
+- Document the `--cap-add` changes in `AGENTS.md` under security.
 
 ### Tier 2 (v2, higher isolation): smokescreen sidecar