docs(readme): the consumer shape, a How to use, and a first CLAUDE.md

[jshvn]

What changes

The README takes the consumer shape used across the org: the lede, How to use (new: how to restore a bundle, where the history and the trash are), How it works (the proton engine's pipeline drawn, this mirror's hooks dashed), Want your own? (fork, storage, secrets, the tokens and the session, prove it), Operating it with a short runbook, Reference. The Proton session commands, the vault setup and the reusable workflow's behaviour are linked to katoptra/lib's README (katoptra/lib#5) rather than repeated. Emoji headings go, as none of the other repositories have them.

• A first CLAUDE.md: the must-knows (reproducible bundles, one token per owner, the session is this mirror's own, public logs) and how to verify a change.
• op.env no longer names the org's vault.

No verb changes; render.txt is untouched.

Storage and operations

None.

Test plan

• task check and task run -- task offline pass (the check workflow)
• The rendered README's diagram draws and its lib links resolve once docs(readme): the manual, with every stage drawn lib#5 merges