Implement TTY detection for Hono's logger middleware

[Goldyvaiiii]

Currently, the logger middleware always applies ANSI color codes regardless of whether
the output destination is a terminal. This causes garbled color escape sequences in
logs when output is piped to files, CI systems, or other non-TTY destinations.

This PR adds cross-runtime TTY detection to getColorEnabled() in src/utils/color.ts:

• Node.js / Bun: checks process.stdout.isTTY
• Deno: checks Deno.stdout.isTerminal() (with legacy isatty() fallback)
• Serverless / Workers: defaults to true (unchanged behavior)

The NO_COLOR env variable continues to take highest precedence.

[Goldyvaiiii]

Adds TTY detection to getColorEnabled() to avoid emitting ANSI colors in non-TTY environments (e.g., CI, piped logs). Supports Node/Bun (process.stdout.isTTY) and Deno (stdout.isTerminal() with fallback). Preserves existing serverless behavior. Updates tests and adds TTY coverage.

[yusukebe]

Related to #3017 #3809

[yusukebe]

Hey @ryuapp @NamesMT

Is this a good time to think of this matter? If we start implementing TTY detection, I think using #3017 is better.

[Goldyvaiiii]

Hey @yusukebe — thanks for the suggestion!

I've updated this PR to align with the centralized TTY detection approach from #3017.

• Added src/utils/flags.ts for environment-based detection
• Refactored getColorEnabled() to use these flags
• Ensured correct precedence for NO_COLOR and FORCE_COLOR
• Updated tests to evaluate the flags dynamically

All tests are passing locally. Please let me know if this direction looks good or if you'd like any further adjustments.

[ryuapp]

Hi.

Is this a good time to think of this matter? If we start implementing TTY detection, I think using #3017 is better.

I agree with the approach #3017 for now. In most cases, it's better to prevent problems from occurring by default.