fix: expand baseline guards for config and flint changes

[zeitlinger]

Summary

• add registry metadata for baseline-trigger config files and unsupported alternate config files
• fail active checks when a known unsupported upstream config is present
• treat .editorconfig as a baseline-triggering config for editorconfig-checker
• expand all active checks when the pinned github:grafana/flint version changes in mise.toml
• document the baseline expansion behavior in CLI and agent knowledge docs

Validation

• FLINT_CASES=general/baseline-flint-upgrade cargo test cases
• mise run lint:fix
• cargo test -q

[Copilot]

Pull request overview

This PR tightens flint’s linter-config handling by explicitly registering baseline-triggering config files and known unsupported upstream/alternate config locations, then failing early when unsupported configs are detected for active checks.

Changes:

• Extend registry Check metadata with baseline_configs and unsupported_configs, plus a ConfigFile descriptor for config detection.
• Add runtime detection: baseline expansion now keys off registered baseline_configs, and flint run hard-fails if an active check’s unsupported_configs are present.
• Add/extend E2E fixtures and docs to cover canonical-config behavior (including .editorconfig triggering baseline for editorconfig-checker).

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/cases/general/unsupported-alternate-config/test.toml	Adds an E2E expectation asserting flint fails on an unsupported alternate shellcheck config.
tests/cases/general/unsupported-alternate-config/files/shellcheckrc	Fixture for an unsupported shellcheck config filename.
tests/cases/general/unsupported-alternate-config/files/mise.toml	Activates shellcheck for the unsupported-config E2E case.
tests/cases/general/unsupported-alternate-config/files/good.sh	Provides a simple shell script input for the E2E case.
tests/cases/general/baseline-editorconfig-change/test.toml	Adds an E2E expectation verifying .editorconfig changes trigger baseline runs for editorconfig-checker.
tests/cases/general/baseline-editorconfig-change/files/mise.toml	Activates editorconfig-checker for the baseline-trigger E2E case.
tests/cases/general/baseline-editorconfig-change/files/hello.txt	Fixture file with trailing whitespace to demonstrate baseline-triggered failure.
tests/cases/general/baseline-editorconfig-change/files/.editorconfig	Baseline .editorconfig version for the baseline-trigger E2E case.
tests/cases/general/baseline-editorconfig-change/changes/.editorconfig	“Changed” .editorconfig used to exercise the baseline expansion path.
src/runner.rs	Updates internal test-only Check literals to include the new Check fields.
src/registry/types.rs	Introduces baseline_configs / unsupported_configs on Check and adds ConfigFile/ConfigMatch types.
src/registry/mod.rs	Re-exports the new config types for use outside the registry module.
src/registry/checks.rs	Registers baseline and unsupported config metadata per built-in linter (including .editorconfig for ec).
src/main.rs	Implements baseline triggering via baseline_configs and adds early failure on detected unsupported configs.
docs/cli.md	Documents baseline triggers beyond the injected config and explains canonical-config enforcement behavior.
.github/agents/knowledge/linters.md	Documents how to register baseline vs unsupported configs when adding linters.
.github/agents/knowledge/architecture.md	Updates architecture notes to reflect baseline triggers and canonical-config enforcement.

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