refactor(neovim): switch CodeCompanion adapter from gemini_cli to codex_acp

Reuses the codex CLI's ChatGPT login (auth_method = "chat-gpt") instead of
gemini's oauth-personal, and disables adapter preset noise in the picker.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

home/emmatherock/neovim.nix

@@ -130,22 +130,23 @@
     plugins.which-key.enable = true;
 
     # --- AI agent: CodeCompanion, curated natively in nixvim ---
-    # Configured to reuse your existing `claude`/`gemini` CLI auth via ACP
+    # Configured to reuse your existing `claude`/`codex` CLI auth via ACP
-    # adapters instead of a separate Anthropic Console API key.
+    # adapters instead of a separate Anthropic Console/OpenAI API key.
     #
     # Verified against https://codecompanion.olimorris.dev/configuration/adapters-acp
     # (CodeCompanion >= v18.0.0, which is what's pinned by nixvim's nixpkgs as of
     # 2026-08). Two things changed from an older/assumed layout:
     #   - the default-adapter key is `interactions.chat.adapter`, not
     #     `strategies.chat.adapter` (renamed in v18.0.0);
-    #   - the built-in adapter names are `claude_code` and `gemini_cli` (no
+    #   - the built-in adapter name is `claude_code` (no `_acp` suffix) and
-    #     `_acp` suffix) and live under `adapters.acp.<name>`.
+    #     lives under `adapters.acp.<name>`.
     #
     # Neither adapter has a true zero-config mode that silently piggybacks on
     # an already-logged-in CLI session:
-    #   - gemini_cli: `defaults.auth_method = "oauth-personal"` reuses the
+    #   - codex_acp: extends the built-in `codex` preset. `defaults.auth_method`
-    #     `gemini` CLI's own login — no key needed, closest thing to "just
+    #     accepts "api-key" | "chat-gpt" (confirmed against the docs above,
-    #     use my existing session".
+    #     not "chatgpt"/"openai-api-key"/"codex-api-key"). "chat-gpt" reuses
+    #     your ChatGPT/Codex CLI login instead of an OPENAI_API_KEY.
     #   - claude_code: there's no oauth-personal equivalent. Run
     #     `claude setup-token` once (ties to your Pro/Max subscription rather
     #     than a Console API key) and save the result to
@@ -155,8 +156,10 @@
     plugins.codecompanion = {
       enable = true;
       settings = {
-        interactions.chat.adapter = "claude_code"; # switch to "gemini_cli" per-chat
+        interactions.chat.adapter = "claude_code"; # switch to "codex_acp" per-chat
+        interactions.inline.adapter = "claude_code";
         adapters.acp = {
+          opts.show_presets = false;
           claude_code.__raw = ''
             function()
               return require("codecompanion.adapters").extend("claude_code", {
@@ -166,16 +169,17 @@
               })
             end
           '';
-          gemini_cli.__raw = ''
+          codex_acp.__raw = ''
             function()
-              return require("codecompanion.adapters").extend("gemini_cli", {
+              return require("codecompanion.adapters").extend("codex", {
                 defaults = {
-                  auth_method = "oauth-personal",
+                  auth_method = "chat-gpt",
                 },
               })
             end
           '';
         };
+        adapters.http.opts.show_presets = false;
           display.chat.window = {
           layout = "vertical";
           position = "right";