feat: preview and confirm before push

`mdcx push` now prints the exact PUT request (URL, masked auth header,
title, version bump, body size delta, and a 20-line body excerpt) and
prompts for confirmation before sending. Add `--yes`/`-y` to skip the
prompt and `--dry-run` to preview only. Non-interactive stdin without
`--yes` errors out instead of hanging.

Splits `Client.UpdateContent` into `BuildUpdate` + send so the CLI can
render the same payload that will be transmitted.

chore: rename module to go.bigb.es/confluence-md-utilities

Move CLI to cmd/mdcx/, add justfile and CLAUDE.md

Restructure to standard Go project layout: merge package cmd
into package main under cmd/mdcx/. Fix .gitignore to use /mdcx
so it only ignores the binary at repo root. Update install path
in README.md.

false

Rename module, add features, fix round-trip fidelity

- Rename module to sourcecraft.dev/bigbes/confluence-md-utilities
- Add fmt command with syntax highlighting (--color=auto/force/disabled)
- Add shell completions for all commands with file extension hints
- Preserve ac:layout/ac:layout-section/ac:layout-cell through round-trips
- Preserve ac:macro-id on code blocks and TOC macros
- Preserve table class/style attributes and colgroup column widths
- Preserve TOC macro as <!-- ac:toc --> comment
- Fix table cell rendering to preserve bold, italic, code, br, links
- Fix user references (ri:userkey) and attachment images (ri:attachment)
- Fix inline spacing between formatting elements in list items

false

Initial commit: mdcx — Markdown to Confluence XML converter

Bidirectional converter between Markdown and Confluence storage format XML
with self-hosted Confluence Server/Data Center sync support.

Features:
- convert: Markdown → Confluence XML
- extract: Confluence XML → Markdown
- embed: embed Markdown into Confluence XML template (marker-based)
- pull/push: sync pages with Confluence via REST API + PAT auth
- fmt: pretty-print Confluence XML with sensible indentation
- Round-trip preservation of inline comments, user refs, attachment images

false