Bug: README uses but CLI only supports (flag docs mismatch)

[Congregalis]

What

README documents long flags like --model, --out, etc. but the CLI is implemented with Go flag package and defines single-dash flags (e.g. -model).

Repro

./transblog --model gpt-5.2 https://example.com
# error: flag provided but not defined: -model (or similar)

Expected

Docs should match reality, OR CLI should accept --flag long form too.

Options

1. Doc-only fix: update README/examples to use -model etc.
2. CLI fix: migrate to pflag (cobra/viper optional) to support GNU-style --model and keep backward compat.

Acceptance criteria

• Choose one approach
• Ensure help output/examples align
• Add a small e2e test for --model if supporting it