Add managed state contract

docs/state-contract.md

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+# State Contract
+
+> Status: draft | Updated 2026-07-06 | Applies to: managed daemon state
+
+AMPG keeps managed daemon state under `gateway.state_dir`. The state contract describes
+which files AMPG owns, which files daemons or adapters write, which paths may contain
+private keys, and which public address files `addresses capture` reads.
+
+## Command
+
+```sh
+python3 -m ampg --config gateway.toml state-contract
+python3 -m ampg --config gateway.toml state-contract --profile mobile-i2p
+python3 -m ampg --config gateway.toml state-contract --protocol tor
+```
+
+Each `AMPG_STATE` row includes:
+
+- `role`: state directory, daemon config, identity key, address file, log file, or similar.
+- `owner`: `ampg`, `daemon`, or `operator`.
+- `required`: whether a managed deployment expects the path.
+- `sensitive`: whether the path may contain private identity material.
+- `path`: resolved path under `gateway.state_dir` unless an adapter documents otherwise.
+
+## Address Capture
+
+`addresses capture` uses the same contract. For each enabled protocol it checks explicit
+`address_file` config first, then contract `address-file` entries in order.
+
+Current managed defaults:
+
+| Protocol | Preferred captured address file | Sensitive identity path |
+| --- | --- | --- |
+| Tor | `<state_dir>/<site>/tor/hidden-service/hostname` | `<state_dir>/<site>/tor/hidden-service` |
+| I2P | `<state_dir>/<site>/i2p/hostname.txt` | `<state_dir>/<site>/i2p/<keys_file>` |
+| Reticulum/IPFS/custom | `<state_dir>/<site>/<protocol>/address.txt` | adapter-specific |
+
+## Safety
+
+AMPG must never delete sensitive contract paths without an explicit destructive command.
+Live apply should copy reviewed config artifacts into their contract `daemon-config`
+paths, start daemons, capture public addresses, and then run published health checks.