docs: describe the unified Agent topology and link controls

Align architecture, protocol, API, storage, security and deployment documentation with default mutual measurements and the Agent link board.

AGENTS.md

@@ -1,13 +1,13 @@
 # Agent Instructions
 
-MoShiro is a self-hosted network path quality monitor. Probes (home broadband) and Agents (public VPS) run active measurements and record raw per-packet and per-event data. The Backend stores it, derives metrics, scores lines per service model, and serves a REST/SSE API to two web apps. Documentation is in Chinese under [`docs/`](docs/); source comments are mostly Chinese too. [`README.md`](README.md) is the entry point.
+MoShiro is a self-hosted network path quality monitor. Agents on home broadband, NAT networks, or public VPS hosts run active measurements and record raw per-packet and per-event data. The Backend stores it, derives metrics, scores lines per service model, and serves a REST/SSE API to two web apps. Documentation is in Chinese under [`docs/`](docs/); source comments are mostly Chinese too. [`README.md`](README.md) is the entry point.
 
 ## Mental model
 
 | Term | Meaning |
 | --- | --- |
-| Probe, Agent | Collector processes (NativeAOT, BCL only). The Probe always dials the Agent; both dial the Backend over `wss` |
-| Line | One (Probe, Agent) pair, per IP family. Id `<agent_id>~<probe_id>`, IPv6 adds `~ipv6`; series key `line:<probe_id>` |
+| Agent | Unified collector process (NativeAOT, BCL only), listening and dialing by default. Each Agent connects to the Backend over `wss` and reports outgoing link health and incoming sessions. |
+| Line | One directed (dialer, listener) Agent pair, per IP family. Id `<agent_id>~<dialer_id>`, IPv6 adds `~ipv6`; series key `line:<dialer_id>` |
 | Kind | A declared measurement method (`udp_echo`, `tcp_echo`, `connect`, ...) composed from building blocks. Defined once in `MoShiro.Protocol/Catalog/Kinds` |
 | RawChunk | Self-describing columnar block, cut every 10 s, appended to segment files. The Backend never trusts node-reported statistics |
 | Metric, Model | `MetricDef` is a one-line declaration over accumulators; models score metrics at query time. Both are recomputable from raw data |
@@ -32,10 +32,11 @@ MoShiro is a self-hosted network path quality monitor. Probes (home broadband) a
 | New measurement method | Kind declaration in `backend/shared/MoShiro.Protocol/Catalog/Kinds`; new building block only if needed in `MoShiro.Measurement/Blocks` plus `BlockCatalog` |
 | New metric | `MetricDef` in `backend/src/MoShiro.Backend.Analysis/Metrics`, add to `MetricRegistry.All` and a preset if shown |
 | New service model | `Analysis/Models` |
-| New RPC method | `MoShiro.Protocol/Rpc` (params, `MoShiroMethodTable`), then `router.On(...)` in `AgentApp` or `ProbeApp`; Backend-side handlers register in `Backend.Gateway` (`FleetGateway`) |
+| New RPC method | `MoShiro.Protocol/Rpc` (params, `MoShiroMethodTable`), then `router.On(...)` in `AgentApp`; Backend-side handlers register in `Backend.Gateway` (`FleetGateway`) |
 | New REST endpoint | `Backend.Api/Public` or `Admin` (typed results, operationId, capability), contract DTO in `Api/Contracts`, then regenerate `backend/openapi/v1.json` and web types |
 | New capability | `Capability` constants in `Backend.Application/Auth/Capabilities.cs`; every `/api/admin` endpoint must declare one |
 | Schema change | Append a migration in `Storage.Sqlite/Schema.cs` and bump `CurrentVersion` |
+| Agent-to-Agent connection states, retry cadence, health reporting | `backend/agent/src/MoShiro.Agent/Dial` (`DialConnection` control layer, `TaskLink` QUIC channel, `LinkStatus`), `LinkHealth` in `MoShiro.Protocol/Rpc`, [`docs/design/architecture.md`](docs/design/architecture.md) §4.3 |
 | Install or update behaviour | `packaging/` (install scripts, Quadlet, compose, updater) and `docs/ops/deployment.md` |
 | Web UI | `web/display` (anonymous read-only), `web/admin`, shared code in `web/shared`. Colors only in `web/shared/theme/tokens.css` |