Move terminal module to terminal-detection crate (#15216)

- Move core/src/terminal.rs and its tests into a standalone
terminal-detection workspace crate.
- Update direct consumers to depend on codex-terminal-detection and
import terminal APIs directly.

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Co-authored-by: Codex <noreply@openai.com>

codex-rs/mcp-server/tests/common/Cargo.toml

@@ -11,6 +11,7 @@ path = "lib.rs"
 anyhow = { workspace = true }
 codex-core = { workspace = true }
 codex-mcp-server = { workspace = true }
+codex-terminal-detection = { workspace = true }
 codex-utils-cargo-bin = { workspace = true }
 rmcp = { workspace = true }
 os_info = { workspace = true }