feat: send spark error output to STDERR

[paulbalandan]

Description

Uncaught exceptions in spark, and errors shown with BaseCommand::showError() or AbstractCommand::renderThrowable() (as migrate and db:seed do), are now printed to STDERR instead of STDOUT, so they no longer mix with output piped to another program or captured by a script. The exit code is unchanged. This also prepares for a --quiet flag, which can then silence STDOUT without hiding errors.

The redirect happens in the exception handler rather than in the CLI error views. The views are copied into every app, so editing them would only reach new projects. Color support is checked against STDERR while redirecting, so 2> err.log does not collect ANSI codes when STDOUT is a terminal.

Scripts that redirect only STDOUT to a log file will no longer capture errors there. The upgrading guide covers this.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[Copilot]

Copilot review overview

🟡 Changes recommended

HTTP command error rendering, STDOUT newline preservation, and test-state cleanup need correction.

Review effort: Balanced
Findings: 1 · 2

Open (3)

• Skip STDERR redirection for non-CLI commands · New
• Restore lastWrite state after redirected writes · New
• Preserve existing NO_COLOR server state during cleanup · New

What changed in this PR

Routes Spark exception output to STDERR, keeping errors separate from piped STDOUT.

Changes:

• Adds scoped redirection with STDERR-aware color detection.
• Adds error-stream tests.
• Documents behavior and logging migration.

Base branch was not supplied; develop compatibility policy was assumed. Validation was limited to source inspection; automated checks remain with CI.

File	Description
user_guide_src/​source/​installation/​upgrade_480.rst	Explains logging migration.
user_guide_src/​source/​cli/​cli_modern_commands.rst	Documents STDERR rendering.
user_guide_src/​source/​cli/​cli_commands.rst	Documents STDERR error output.
user_guide_src/​source/​changelogs/​v4.8.0.rst	Records the behavior change.
tests/​system/​Debug/​ExceptionHandlerTest.php	Checks exception output routing.
tests/​system/​CLI/​CLITest.php	Tests redirection and colors.
tests/​system/​CLI/​BaseCommandTest.php	Checks STDERR error rendering.
tests/​system/​CLI/​AbstractCommandTest.php	Checks STDERR throwable rendering.
system/​Debug/​ExceptionHandler.php	Redirects CLI exception rendering.
system/​CLI/​CLI.php	Adds scoped stream redirection.
system/​CLI/​BaseCommand.php	Redirects command error views.

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