Ship a single-file output mode (stdout / -out -) for piping + scripts

[Congregalis]

Why

TransBlog is a CLI, but right now it always writes into ./out/ (or -out path). For quick workflows (e.g. pipe into another tool, preview, diff, or commit), stdout output is a big UX win.

Proposal

• Support -out - to write translated Markdown to stdout (single URL only).
• If -view is enabled, either:
  • disallow with -out - (explicit error), or
  • print HTML to stdout and disable writing markdown file.
• When -out - is used: do not create state/summary files unless explicitly requested.

Acceptance Criteria

• transblog -out - <url> writes the markdown to stdout
• Exit codes unchanged
• Tests cover stdout mode

Notes

This enables easy usage like:

transblog -out - https://example.com/post | glow -