docs: record architecture decisions (ADR-0001..0009) and operations knowledge

Add docs/adr/ with a chronological ADR set reconstructed from the project
history (no orchestrator, one storage format, derived-state sync,
SQL-over-SSH contract, WireGuard beneath SSH, IaC boundaries, non-root
image, runtime data paths, bounded lake scans), an index README, and a
template. Distinguish repo-local ADRs from ecosystem-wide ASRs.

Expand AGENTS.md with a decision-records section and a runtime/operations
guide (service URLs, rebuild workflow, CPU budget knobs). Reference the
ADRs from README, CONTRIBUTING, and the affected design docs, and add an
open question for T1 partition pruning.

docs/adr/ADR-0002-one-storage-format.md

@@ -0,0 +1,32 @@
+# ADR-0002: One storage format on every tier — Parquet + DuckDB, Hive layout
+
+## Status
+
+Accepted (2026-07-08)
+
+## Context
+
+Data lives in three places: on the drone's NVMe in flight (T1), in the ground
+warehouse after landing (T3), and in the dev/simulation environment. If each
+tier used a different format or layout, offload would need transformation code,
+schemas would drift, and a query proven on the bench would not run unchanged on
+flight data.
+
+## Decision
+
+Use **one storage format on every floor**: columnar **Parquet** files in an
+identical **Hive-partitioned** layout (`dataset=…/flight=…/drone=…/…`), queried
+with **DuckDB**. Flight offload T1 → T3 is therefore a plain **mirror**
+(copy/rsync of partition directories), not an ETL step.
+
+## Consequences
+
+- Offload is a file operation, testable with a checksum; no format converters
+  to maintain or version.
+- The same SQL runs against T1, T3, and simulated data — the simulator
+  ([`../../simulator/`](../../simulator/)) generates the *real* layout, so tests
+  exercise the production format.
+- Partitioning choices are load-bearing; changing them is a schema migration.
+  Detailed in [`../03-data-platform.md`](../03-data-platform.md).
+- DuckDB's single-file, no-server model fits an air-gapped drone with no room
+  for a database daemon.