feat: checkpoint device agent runtime milestones

docs/adr/0001-device-agnostic-runtime.md

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+# ADR 0001: Device-Agnostic Runtime
+
+## Status
+
+Accepted
+
+## Context
+
+The project began as Apex Agent, centered on iPhone automation. The existing
+MVP already has a driver-independent `Driver` interface, WDA as the first
+driver, device lifecycle management, scene perception, runtime execution, task
+memory, and REST/MCP surfaces. The old names and package layout still implied
+that iPhone/WDA was the platform rather than the first adapter.
+
+The OpenSpec change `device-agent-runtime-foundation` records the detailed
+design decisions for this repositioning.
+
+## Decision
+
+Reposition the project as Device Agent Runtime:
+
+- Keep `core/` for shared domain models and errors.
+- Move the driver contract and concrete drivers into `driver/`.
+- Move device lifecycle management into `device/`.
+- Rename `vision/` to `perception/`.
+- Move driver-type factory selection into `driver/registry.py`.
+- Rename the shared error base to `DeviceRuntimeError`.
+- Treat iPhone/WDA as the first driver, not the product boundary.
+
+## Alternatives Considered
+
+Keeping the old Apex Agent/iPhone framing was rejected because it would make
+future Android, browser, desktop, and cloud-device support look like exceptions
+instead of first-class adapters.
+
+Eliminating `core/` entirely was rejected for this change because models such
+as `Scene`, `Task`, and `Device` are shared across several layers today.
+Forcing them into `perception/` or `runtime/` would add coupling without
+behavioral value.
+
+Keeping a deprecated `ApexAgentError` alias was rejected because there are no
+external consumers to preserve yet.
+
+## Consequences
+
+Future driver support is added in the driver layer and registry. Future
+perception techniques are added behind `PerceptionProvider`. User-facing
+runtime behavior remains unchanged, while package names and docs now match the
+device-agnostic direction.