Format large numbers in a more readable way. (#2046)

- In the bottom line of the TUI, print the number of tokens to 3 sigfigs
  with an SI suffix, e.g. "1.23K".
- Elsewhere where we print a number, I figure it's worthwhile to print
  the exact number, because e.g. it's a summary of your session. Here we print
  the numbers comma-separated.

codex-rs/protocol/Cargo.toml

@@ -12,6 +12,8 @@ workspace = true
 
 [dependencies]
 base64 = "0.22.1"
+icu_decimal = "2.0.0"
+icu_locale_core = "2.0.0"
 mcp-types = { path = "../mcp-types" }
 mime_guess = "2.0.5"
 serde = { version = "1", features = ["derive"] }
@@ -20,6 +22,7 @@ serde_json = "1"
 serde_with = { version = "3.14.0", features = ["macros", "base64"] }
 strum = "0.27.2"
 strum_macros = "0.27.2"
+sys-locale = "0.3.2"
 tracing = "0.1.41"
 ts-rs = { version = "11", features = ["uuid-impl", "serde-json-impl"] }
 uuid = { version = "1", features = ["serde", "v4"] }