feat(cli): make tree the sole default for glint graph

Previously glint graph with no mode printed tree + separator + includes
Mermaid. Now glint graph defaults to tree only; use glint graph includes
for the Mermaid include-dependency output. Simplifies the common case
and makes the default output immediately actionable.

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

README.md

@@ -21,7 +21,7 @@ A local tool to validate and lint `.gitlab-ci.yml` pipelines without needing a G
 - **Simulates context** — `--branch`, `--tag`, `--source` flags evaluate `rules:if:` and `only`/`except` to show which jobs would be active, manual, or skipped; `--context branch=main --context branch=develop` prints a multi-column comparison table across multiple contexts in one run
 - **Multiple output formats** — `--format text` (default, colorized and column-aligned), `json`, `sarif` (GitHub Code Scanning / GitLab SAST), `junit`, `github` (PR annotations); exits `2` on errors, `10` on warnings only
 - **Project config** — `.glint.yml` for rule suppression, severity overrides, token/URL/proxy defaults; `# glint: ignore RULE` for per-job inline suppression; `--no-warn` flag to suppress all warnings
-- **Graph visualization** — `glint graph` prints a terminal job tree; `glint graph pipeline` renders a GitLab CI-style SVG/PNG; `--format mermaid` emits a Mermaid flowchart; `--format html` produces a self-contained HTML file with pan/zoom and a job-detail sidebar; `--no-skipped` hides jobs that would not run in the given context
+- **Graph visualization** — `glint graph` prints a terminal job tree (default); `glint graph includes` emits a Mermaid include-dependency graph; `glint graph pipeline` renders a GitLab CI-style SVG/PNG; `--format mermaid` or `--format html` for alternative pipeline output; `--no-skipped` hides jobs that would not run in the given context
 - **LSP server** — `glint lsp` starts a Language Server Protocol server over stdin/stdout; connect with any LSP client to get inline diagnostics (rule ID as code, error/warning severity) in VS Code, Neovim, Emacs, JetBrains, etc.
 - **VS Code extension** — `editors/vscode/` wraps the LSP server; inline squiggles for every glint rule directly in the editor