Handle FORCE_COLOR values like Node

[Jake Bailey (jakebailey)]

Fixes #63888

[Copilot]

Pull request overview

Updates compiler CLI color detection to match Node.js FORCE_COLOR, NO_COLOR, TERM, and TTY behavior.

Changes:

• Distinguishes unset environment variables from empty values.
• Implements Node-compatible color precedence and accepted values.
• Adds command-line regression coverage for color handling.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tsc/cmd/tsc/sys.go	Uses os.LookupEnv to preserve environment-variable presence.
tsc/internal/execute/tsc/compile.go	Updates the system environment API.
tsc/internal/execute/tsc/diagnostics.go	Implements Node-compatible color selection.
tsc/internal/execute/tsc/emit_test.go	Updates test systems for the environment API.
tsc/internal/execute/tsctests/runner.go	Adds configurable TTY state to tests.
tsc/internal/execute/tsctests/sys.go	Simulates environment presence and TTY output.
tsc/internal/execute/tsctests/tsc_test.go	Adds color-environment test scenarios.
tsc/internal/execute/watcher.go	Adapts watch debugging to the new API.
tsc/internal/execute/build/orchestrator.go	Adapts build-watch debugging to the new API.
tsc/testdata/baselines/reference/tsc/commandLine/FORCE_COLOR-overrides-NO_COLOR.js	Verifies FORCE_COLOR precedence.
tsc/testdata/baselines/reference/tsc/commandLine/FORCE_COLOR-overrides-dumb-TERM.js	Verifies forced color with a dumb terminal.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-TERM-is-dumb.js	Verifies dumb-terminal suppression.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-NO_COLOR-is-set.js	Verifies NO_COLOR suppression.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-NO_COLOR-is-set-even-if-FORCE_COLOR-is-set.js	Removes the obsolete precedence baseline.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-FORCE_COLOR-is-zero.js	Verifies FORCE_COLOR=0.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-FORCE_COLOR-is-invalid.js	Verifies invalid values disable color.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-FORCE_COLOR-is-four.js	Verifies unsupported color level handling.
tsc/testdata/baselines/reference/tsc/commandLine/does-not-add-color-when-FORCE_COLOR-is-false.js	Verifies FORCE_COLOR=false.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-NO_COLOR-is-empty.js	Verifies empty NO_COLOR handling.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-two-and-output-is-not-a-TTY.js	Verifies forced level-two color.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-true-and-output-is-not-a-TTY.js	Verifies forced color using true.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-three-and-output-is-not-a-TTY.js	Verifies forced level-three color.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-one-and-output-is-not-a-TTY.js	Verifies forced level-one color.
tsc/testdata/baselines/reference/tsc/commandLine/adds-color-when-FORCE_COLOR-is-empty-and-output-is-not-a-TTY.js	Verifies empty FORCE_COLOR enables color.

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