Support Codex OAuth login and add CLI setup docs

CODEX_SETUP.md

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+# Connecting Hermes MCP to Codex CLI
+
+Hermes is exposed for Codex at:
+
+```text
+https://hermes.squaremcp.com/mcp
+```
+
+## Recommended setup
+
+Add this block to your global Codex config at:
+
+```text
+~/.codex/config.toml
+```
+
+```toml
+[mcp_servers.hermes]
+url = "https://hermes.squaremcp.com/mcp"
+```
+
+If the file already exists, append or merge the block instead of replacing your other config.
+
+## Example
+
+```toml
+[projects."/path/to/your/project"]
+trust_level = "trusted"
+
+[mcp_servers.hermes]
+url = "https://hermes.squaremcp.com/mcp"
+```
+
+## Auth model
+
+Hermes supports:
+
+1. `x-api-key`
+2. `?key=`
+3. OAuth bearer tokens
+
+Codex config currently uses the server URL block above. If your Codex build later exposes MCP header configuration directly, use your own live credential and do not commit it into this repo.
+
+## Verify
+
+After updating `~/.codex/config.toml`, restart Codex and check that the `hermes` MCP server is available in the tool space for the project.
+
+## Current production endpoint
+
+```text
+https://hermes.squaremcp.com/mcp
+```
+
+## Related docs
+
+1. [CLI agent setup](./AGENTS_CLI_SETUP.md)
+2. [opencode setup](./OPENCODE.md)
+3. [ChatGPT setup](./CHATGPT_SETUP.md)