docs: make the packaged DocStripper quickstart preview-first

[kiku-jw]

Why

The tap README repeats in-place DOCX/PDF examples and describes the command-line package as broadly AI-powered. Its actual formula installs upstream v2.1.0, not the current default branch.

Changes

• Describe this repository as a Homebrew distribution surface for the rule-based CLI; keep the optional browser AI mode separate.
• Start both examples with --dry-run.
• Warn that the packaged version writes plain text to its input path in normal mode, including DOCX/PDF paths, and that --stdout also contains diagnostics.
• Link the formula and the exact v2.1.0 source so package behavior is not confused with future upstream changes.

Verification

Read the complete tap README and recursive tree, Formula/docstripper.rb, and the actual upstream tool.py at the formula's v2.1.0 tag (write/backup/stdout paths and argument dispatch). --dry-run and --stdout are present in that tagged source. The formula, version, checksum, dependencies, install command and license are unchanged. No Homebrew installation, CLI execution or runtime tests were performed.

Secrets check: reviewed the documentation changes; no real secrets added.

This README-only PR complements KikuAI-Lab/DocStripper#15. Neither PR fixes the CLI implementation or publishes a new package. No repository settings, CI, releases, deployment, merge or auto-merge changes are requested.

[chatgpt-codex-connector]

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