Device binding contract: versioned range plan from onggi diff (ADR-0010) #75

Problem

onggi diff --ranges --json is already what a runtime consumes to update only the bytes that changed between two
variants (#46; rngd-pd resident delta). But the output has no schema name or version, the per-range class is implicit
(only the changed [offset, length] runs are listed, without saying whether a run is elsewhere in the base or new, or
where in the base its bytes lie), and nothing written down says what a runtime may assume or must do with it. Each
runtime integration therefore reads the output its own way.

In the design, only two parts are vendor-specific: the publisher-declared variant coordinate and the device
binding that maps byte ranges to device memory. The binding needs one explicit, versioned contract.

Scope

• ADR docs/adr/0010-device-binding-contract.md (status: proposed): the range plan of onggi diff --ranges --json is
  the only interface between onggi and a runtime; its fields (file, base file, offset, length, kind
  same/elsewhere/new, source offset in the base for elsewhere); the binding's obligations (map to whole device
  rows or request a full reload; verify; roll back).
• Give the JSON output an explicit schema name/version and a per-range list with kinds, keeping the existing fields so
  current consumers keep working.

Out of scope: runtime code (rngd-pd), any vendor-specific mapping.

Done when

• ADR-0010 merged as proposed
• onggi diff --ranges --json carries schema and the typed range plan; old fields unchanged (test)
• CI green