feat(cli)!: subcommand CLI, graph tree mode, local include resolution

BREAKING CHANGES:
- `glint <file>` removed; use `glint check <file>`
- `--graph <mode>` removed; use `glint graph [mode]`
- `--graph-out` renamed to `--out` on `glint graph`

feat(cli): ruff-style subcommands — `glint check` and `glint graph [mode]`
feat(graph): `glint graph tree` — terminal job tree with context annotations
feat(graph): context flags (--branch/--tag/--source/--var) on `glint graph`
feat(resolver): recursive local include resolution from disk
fix(resolver): extends unknown base emits warning instead of fatal error
fix(model): script/before_script/after_script accept block scalar string form
test(linter): Samba project CI fixtures as integration tests
chore(build): fix .gitignore to not exclude cmd/glint/ directory
docs: update CHANGELOG, README, ROADMAP for v0.2.0

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

internal/linter/linter.go

@@ -88,7 +88,7 @@ func checkJob(name string, job model.Job, stageSet map[string]bool) []Finding {
 
 	// After extends resolution, a job with no script/run is an error.
 	// Exceptions: trigger jobs, pages jobs (use pages: keyword), and template jobs.
-	hasScript := len(job.Script) > 0 || job.Run != nil
+	hasScript := scriptNonEmpty(job.Script) || job.Run != nil
 	if !isTemplate && !isTrigger && job.Pages == nil && !hasScript {
 		findings = append(findings, Finding{
 			Severity: Error,
@@ -139,3 +139,15 @@ func checkJob(name string, job model.Job, stageSet map[string]bool) []Finding {
 
 	return findings
 }
+
+// scriptNonEmpty reports whether a script/before_script/after_script field
+// (which may be a []any list or a plain string) is non-empty.
+func scriptNonEmpty(v any) bool {
+	switch s := v.(type) {
+	case []any:
+		return len(s) > 0
+	case string:
+		return s != ""
+	}
+	return false
+}