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>

samba-testdata/.gitlab-ci-private.yml

@@ -0,0 +1,5 @@
+# This is just a legacy alias used by the
+# https://gitlab.com/samba-team/devel/samba configuration
+#
+include:
+  - '/.gitlab-ci.yml'