Design notes

Long-form architectural rationale for Pulse subsystems where the choice wasn't obvious. These are the documents you read once before you make a PR that changes the subsystem.

Note	Subsystem
Design principles	All of Pulse — start here.
Multi-tenant context	features/multi-tenant.md

More design notes will be added as subsystems evolve. If you're proposing a non-trivial change to an existing subsystem, the convention is "post the design note as the first PR, then the implementation."