Envelope errors[].category isn't the coarse category the docs promise #699

Problem

docs/cli.md says each envelope error carries "a coarse category", and its table lists one category per exit family (general, config, input, template, llm, github, git, version, publish). But categoryForCode (packages/core/src/envelope.ts ~87) derives the category from the specific code:

So category is just the code reformatted, not a coarse grouping. An agent that branches on category gets an open-ended set of values instead of the nine documented ones. This has been visible since #651, when release/standing-pr started reporting stage codes, and #616 (enveloping version/publish) adds more.

Found during the #616 review (round 3), verified with the built CLIs.

Options

1. Make it coarse: derive category from the code's exit family. feat(cli)!: envelope the version and publish commands, unwrap on the pipe #616 adds CODE_TO_EXIT, a complete code → family table, which is the natural source. A changed category value is a contract change for consumers, so decide whether it needs a schemaVersion bump or a release-notes callout.
2. Make the docs match: say category is a slug of the code, and point readers at the exit code for the family.

Option 1 matches what the contract was meant to give agents.