plan-a-phased-build

## Project Context - CLAUDE.md: !`find . -maxdepth 1 -name "CLAUDE.md" -type f` - project-discovery.md: !`find . -maxdepth 3 -name "project-discovery.md" -type f` ## Operating Principles - **Plain language is the default surface.** The build-phase outline never contains file paths, line numbers, function or class names, library mechanics, or language primitives. It uses product-level subsystem names ("the events processing system", "the database"), user-facing UI vocabulary (popover, modal, toast), behavioral verbs (publishes, retries, expires), and user-observable states. Brand names generalize one level up — "PostgreSQL" → "the database", "NATS JetStream" → "the events processing system". A non-technical stakeholder must be able to read the document end-to-end. - **Every phase must be demonstrable to a real person.** "Demonstrable" means a person can be put in front of the running result and see something happen end-to-end — not "we shipped a service", but "you can do X and Y happens". If a phase is not demoable, it is either too small (merge it forward into the next phase that does become demoable) or too horizontal (it is a layer, not a slice — re-think it as a thinner end-to-end strip). - **Every phase builds on the prior.** As phases ship, the system becomes progressively more capable. Earlier phases stay valid; later phases enrich what earlier ones delivered. Never sequence a phase so that it invalidates an earlier deliverable. - **Vertical slices, not horizontal la...