fix: auto-detect color support from environment and TTY
Disable color output automatically when the environment indicates it
is not appropriate. Previously, Console.Color was hardcoded to true
regardless of context.
Color is now disabled when any of the following are true:
- NO_COLOR env var is set (per https://no-color.org/)
- COG_NO_COLOR env var is set
- TERM=dumb
- stderr is not an interactive terminal (TTY)
The TTY check is on stderr specifically, since that is where cog
writes all its colored log output.
Refs: https://clig.dev/#output, https://no-color.org/
