Fix agent host CLI output issues for Windows

[Dmitriy Vasyura (dmitrivMS)]

This pull request addresses several output issues in the Agent Host CLI on Windows, specifically related to improper character rendering and incorrect branding.

Changes include:

• Updated the output formatting to use ASCII characters instead of Unicode for banners and symbols in output.rs, ensuring compatibility with Windows consoles.
• Corrected the application name from code to code-insiders in agent_host.rs to reflect the correct branding.
• Centralized the UTF-8/ASCII selection logic for all user-visible symbols across commands, including agent ps and agent logs.
• Implemented detection of the terminal's UTF-8 support using GetConsoleOutputCP() to dynamically adjust output formatting.

All changes have been validated with passing tests and proper formatting.

Fixes #333375

[Copilot]

Copilot review overview

Review tier: Balanced
Findings: None

What changed in this PR

Updates Agent Host CLI output for Windows console compatibility and correct product branding.

Changes:

• Selects Unicode or ASCII decorations based on Windows console encoding.
• Propagates terminal capability to detached supervisors.
• Uses the configured application name in management commands and safely truncates Unicode text.

File	Description
cli/​src/​tunnels/​code_server.rs	Uses the encoding-safe banner marker.
cli/​src/​commands/​output.rs	Centralizes symbol selection and Windows UTF-8 detection.
cli/​src/​commands/​agent_ps.rs	Adds ASCII-safe status and warning symbols.
cli/​src/​commands/​agent_logs.rs	Adds ASCII-safe decorations and Unicode-safe truncation.
cli/​src/​commands/​agent_host.rs	Corrects command branding and propagates encoding capability.

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