feat(cli): .glint.yml config and inline suppression comments

Adds project-level configuration and per-job suppression directives:

.glint.yml (searched from pipeline dir up to the git root):
- ignore: [GL007, GL032] — suppress rules globally for the project
- severity: {GL004: warning} — override rule severity (error/warning/ignore)
- stages: [quality] — extra stages beyond the pipeline's stages: block
- token: / url: / cache_dir: — defaults for flags; lower priority than
  CLI flags and environment variables

Inline suppression (# glint: ignore):
- Place "# glint: ignore GL007" immediately before a job definition to
  suppress that rule for the specific job only
- Multiple rules: "# glint: ignore GL007, GL032" (comma or space separated)
- Wildcard: "# glint: ignore all" suppresses every finding for the job
- Suppressions are scoped to the annotated job; pipeline-level findings
  are unaffected
- Parsed from yaml.Node head/line comments in the first parse pass;
  stored in Pipeline.Suppressions (root file only, not includes)

New packages: internal/config (Load, walk-up search, .git boundary stop)
New files: cmd/glint/filter.go (applyConfig, isSuppressed helpers)
Tests: config_test.go, parser_suppress_test.go, filter_test.go
Validate fixtures: testdata/config_ignored/, config_severity/, config_suppress/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/config/config_test.go

@@ -0,0 +1,112 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLoad_NotFound(t *testing.T) {
+	tmp := t.TempDir()
+	cfg, err := Load(tmp)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(cfg.Ignore) != 0 || cfg.Token != "" || cfg.URL != "" {
+		t.Errorf("expected empty config, got %+v", cfg)
+	}
+}
+
+func TestLoad_Found(t *testing.T) {
+	tmp := t.TempDir()
+	content := `
+ignore:
+  - GL007
+  - GL032
+severity:
+  GL004: warning
+stages:
+  - quality
+token: glpat-test
+url: https://gitlab.example.com
+cache_dir: /tmp/glint-cache
+`
+	if err := os.WriteFile(filepath.Join(tmp, Filename), []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := Load(tmp)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(cfg.Ignore) != 2 || cfg.Ignore[0] != "GL007" {
+		t.Errorf("ignore = %v", cfg.Ignore)
+	}
+	if cfg.Severity["GL004"] != "warning" {
+		t.Errorf("severity = %v", cfg.Severity)
+	}
+	if len(cfg.Stages) != 1 || cfg.Stages[0] != "quality" {
+		t.Errorf("stages = %v", cfg.Stages)
+	}
+	if cfg.Token != "glpat-test" {
+		t.Errorf("token = %q", cfg.Token)
+	}
+	if cfg.URL != "https://gitlab.example.com" {
+		t.Errorf("url = %q", cfg.URL)
+	}
+	if cfg.CacheDir != "/tmp/glint-cache" {
+		t.Errorf("cache_dir = %q", cfg.CacheDir)
+	}
+}
+
+func TestLoad_WalksUp(t *testing.T) {
+	tmp := t.TempDir()
+	sub := filepath.Join(tmp, "subdir", "pipeline")
+	if err := os.MkdirAll(sub, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// Config at the top-level (no .git, so walk continues to tmp).
+	if err := os.WriteFile(filepath.Join(tmp, Filename), []byte("token: walked-up\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := Load(sub)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if cfg.Token != "walked-up" {
+		t.Errorf("token = %q, want walked-up", cfg.Token)
+	}
+}
+
+func TestLoad_StopsAtGitRoot(t *testing.T) {
+	tmp := t.TempDir()
+	sub := filepath.Join(tmp, "repo", "src")
+	if err := os.MkdirAll(sub, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// .git marks the repo root — walk must stop here.
+	if err := os.Mkdir(filepath.Join(tmp, "repo", ".git"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// Config placed ABOVE the .git root should not be found.
+	if err := os.WriteFile(filepath.Join(tmp, Filename), []byte("token: should-not-load\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	cfg, err := Load(sub)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if cfg.Token != "" {
+		t.Errorf("token = %q, should not have crossed .git boundary", cfg.Token)
+	}
+}
+
+func TestLoad_InvalidYAML(t *testing.T) {
+	tmp := t.TempDir()
+	if err := os.WriteFile(filepath.Join(tmp, Filename), []byte("ignore: [unclosed\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	_, err := Load(tmp)
+	if err == nil {
+		t.Error("expected error for invalid YAML")
+	}
+}