v0.26.0

• Render Markdown help from the shared help model instead of the argument parser's own help writer, so --output selects a format and never a different set of commands or arguments
• Make the Markdown export real Markdown — heading, prose, usage, and argument/subcommand tables — instead of concatenated terminal help blocks with no Markdown structure
• Add a gate check asserting that json, plain, and markdown describe the same commands and the same arguments at one scope, verified against a reintroduced regression
• Drop the -0 alias for --null on paths and keys: a short flag that merely abbreviates a flag of afdata's own invention, which the convention's own rule rejects
• Document --null where a reader meets it, in the Bash authoring guide and the README, including why line-separated output is unsafe when a JSON key contains a newline
• Fix the spec's short-flag example to cite imitation of an established interface rather than an abbreviation of afdata's own flag