feat(routing): Phase 1.3 — RPC observability, relay session reuse, tombstone hardening

Routing table fixes:
- Tombstone entries now set ExpiresAt on withdrawal (RemoveDirectPeer,
  InvalidateTransitRoutes) so TickTTL cleans them after TTL instead of
  immediately or never
- Same-SeqNo updates can no longer resurrect withdrawn routes — only
  strictly newer SeqNo from the origin supersedes a tombstone
- IsExpired boundary fix: exact-boundary timestamps now correctly
  treated as expired (!now.Before instead of now.After)

Relay key sync:
- New syncSenderKeys() reuses existing outbound session for on-demand
  key fetch instead of opening a fresh TCP connection
- handleRelayMessage accepts optional syncSession parameter to avoid
  deadlock on single-reader inboxCh when called from within session loop
- syncPeer auth phase skips up to 5 interleaved non-auth frames
  (announce_routes race during handshake)

RPC routing observability:
- New routing_commands.go: fetch_route_table, fetch_route_summary,
  fetch_route_lookup with RoutingProvider interface
- New routing_provider.go: bridges node.Service to RPC layer
- PeerTransport filters out disconnected peers via health check
- Console parser rejects extra arguments for no-arg routing commands
- snapshot_at field added to fetch_route_summary response
- Full handler test coverage (handler_routing_test.go)

Documentation:
- Roadmap rewritten to reflect current state (three delivery mechanisms)
- Diagram updated: Node D shows routing-table-based path selection
- New docs/rpc/routing.md with full field specs (EN + RU)
- routing.md updated with snapshot_at and tombstone semantics

Author: gades

docs/roadmap.md

@@ -175,6 +175,7 @@ graph TD
     REG_NTC["RegisterNoticeCommands<br/>fetch_notices"]
     REG_MSH["RegisterMeshCommands<br/>fetch_relay_status"]
     REG_MET["RegisterMetricsCommands<br/>fetch_traffic_history"]
+    REG_RTE["RegisterRoutingCommands<br/>fetch_route_table · fetch_route_summary · fetch_route_lookup*"]
 
     REG_SYS -->|"Register()"| TABLE
     REG_NET -->|"Register()"| TABLE
@@ -184,16 +185,18 @@ graph TD
     REG_NTC -->|"Register()"| TABLE
     REG_MSH -->|"Register()"| TABLE
     REG_MET -->|"Register()"| TABLE
+    REG_RTE -->|"Register()"| TABLE
 
     TABLE --> SERVER["Fiber HTTP Server<br/>(wraps CommandTable)"]
     TABLE --> WINDOW["Desktop Window<br/>(direct access)"]
 
     style REG_CHT fill:#555,stroke:#888
     style REG_MSG fill:#555,stroke:#888
+    style REG_RTE fill:#555,stroke:#888
 ```
 *Diagram 4 — Command registration.*
 
-Commands marked with `*` are mode-gated: when their provider is nil (standalone node), they are registered as unavailable via `RegisterUnavailable()` — returning 503 and hidden from help. `send_dm` requires DMRouterProvider; chatlog commands require ChatlogProvider; `fetch_traffic_history` requires MetricsProvider.
+Commands marked with `*` are mode-gated: when their provider is nil (standalone node), they are registered as unavailable via `RegisterUnavailable()` — returning 503 and hidden from help. `send_dm` requires DMRouterProvider; chatlog commands require ChatlogProvider; `fetch_traffic_history` requires MetricsProvider; routing commands require RoutingProvider.
 
 ### Configuration
 
@@ -222,7 +225,7 @@ The architecture separates command execution from transport:
 // CommandTable — single source of truth for all commands.
 // RegisterAllCommands is the single registration point — both bootstrap and tests use it.
 table := rpc.NewCommandTable()
-rpc.RegisterAllCommands(table, nodeService, chatlogProvider, dmRouter, metricsCollector)
+rpc.RegisterAllCommands(table, nodeService, chatlogProvider, dmRouter, metricsCollector, routingProvider)
 
 // Desktop: replace base ping/get_peers with diagnostic-enriched versions,
 // and hello with desktop identity (Client: "desktop").
@@ -250,6 +253,7 @@ server, _ := rpc.NewServer(cfg, table, nodeService)
 | **notice** | fetch_notices | Always registered |
 | **mesh** | fetch_relay_status | Always registered |
 | **metrics** | fetch_traffic_history | Always registered; unavailable (503, hidden from help) when MetricsProvider is nil |
+| **routing** | fetch_route_table, fetch_route_summary, fetch_route_lookup | Always registered; unavailable (503, hidden from help) when RoutingProvider is nil |
 
 #### Dependency Injection
 
@@ -302,6 +306,7 @@ Per-command documentation is in the [rpc/](rpc/) folder. See [rpc/README.md](rpc
 | [Notice](rpc/notice.md) | `fetch_notices` | [rpc/notice.md](rpc/notice.md) |
 | [Mesh](rpc/mesh.md) | `fetch_relay_status` | [rpc/mesh.md](rpc/mesh.md) |
 | [Metrics](rpc/metrics.md) | `fetch_traffic_history` | [rpc/metrics.md](rpc/metrics.md) |
+| [Routing](rpc/routing.md) | `fetch_route_table`, `fetch_route_summary`, `fetch_route_lookup` | [rpc/routing.md](rpc/routing.md) |
 
 ### corsa-cli
 
@@ -597,6 +602,7 @@ graph TD
     REG_NTC["RegisterNoticeCommands<br/>fetch_notices"]
     REG_MSH["RegisterMeshCommands<br/>fetch_relay_status"]
     REG_MET["RegisterMetricsCommands<br/>fetch_traffic_history"]
+    REG_RTE["RegisterRoutingCommands<br/>fetch_route_table · fetch_route_summary · fetch_route_lookup*"]
 
     REG_SYS -->|"Register()"| TABLE
     REG_NET -->|"Register()"| TABLE
@@ -606,16 +612,18 @@ graph TD
     REG_NTC -->|"Register()"| TABLE
     REG_MSH -->|"Register()"| TABLE
     REG_MET -->|"Register()"| TABLE
+    REG_RTE -->|"Register()"| TABLE
 
     TABLE --> SERVER["Fiber HTTP сервер<br/>(обёртка над CommandTable)"]
     TABLE --> WINDOW["Desktop Window<br/>(прямой доступ)"]
 
     style REG_CHT fill:#555,stroke:#888
     style REG_MSG fill:#555,stroke:#888
+    style REG_RTE fill:#555,stroke:#888
 ```
 *Диаграмма 4 — Регистрация команд.*
 
-Команды с `*` являются mode-gated: при nil-провайдере (standalone нода) они регистрируются как недоступные через `RegisterUnavailable()` — возвращают 503 и скрыты из help. `send_dm` требует DMRouterProvider; chatlog-команды требуют ChatlogProvider; `fetch_traffic_history` требует MetricsProvider.
+Команды с `*` являются mode-gated: при nil-провайдере (standalone нода) они регистрируются как недоступные через `RegisterUnavailable()` — возвращают 503 и скрыты из help. `send_dm` требует DMRouterProvider; chatlog-команды требуют ChatlogProvider; `fetch_traffic_history` требует MetricsProvider; routing-команды требуют RoutingProvider.
 
 ### Конфигурация
 
@@ -644,7 +652,7 @@ graph TD
 // CommandTable — единственный источник истины для всех команд.
 // RegisterAllCommands — единая точка регистрации, используемая и bootstrap, и тестами.
 table := rpc.NewCommandTable()
-rpc.RegisterAllCommands(table, nodeService, chatlogProvider, dmRouter, metricsCollector)
+rpc.RegisterAllCommands(table, nodeService, chatlogProvider, dmRouter, metricsCollector, routingProvider)
 
 // Desktop: замена базовых ping/get_peers на диагностически обогащённые версии,
 // а также hello на desktop-идентификацию (Client: "desktop").
@@ -672,6 +680,7 @@ server, _ := rpc.NewServer(cfg, table, nodeService)
 | **notice** | fetch_notices | Всегда зарегистрированы |
 | **mesh** | fetch_relay_status | Всегда зарегистрированы |
 | **metrics** | fetch_traffic_history | Всегда зарегистрирована; недоступна (503, скрыта из help) при MetricsProvider = nil |
+| **routing** | fetch_route_table, fetch_route_summary, fetch_route_lookup | Всегда зарегистрированы; недоступны (503, скрыты из help) при RoutingProvider = nil |
 
 #### Внедрение зависимостей
 
@@ -724,6 +733,7 @@ Mode-gated команды регистрируются через `RegisterUnava
 | [Уведомления](rpc/notice.md) | `fetch_notices` | [rpc/notice.md](rpc/notice.md) |
 | [Mesh](rpc/mesh.md) | `fetch_relay_status` | [rpc/mesh.md](rpc/mesh.md) |
 | [Метрики](rpc/metrics.md) | `fetch_traffic_history` | [rpc/metrics.md](rpc/metrics.md) |
+| [Маршрутизация](rpc/routing.md) | `fetch_route_table`, `fetch_route_summary`, `fetch_route_lookup` | [rpc/routing.md](rpc/routing.md) |
 
 ### corsa-cli
 

docs/roadmap.ru.md

@@ -16,6 +16,7 @@ Per-command-group documentation for the CORSA RPC layer. For architecture overvi
 | [Notice](notice.md) | `fetch_notices` | [notice.md](notice.md) |
 | [Mesh](mesh.md) | `fetch_relay_status` | [mesh.md](mesh.md) |
 | [Metrics](metrics.md) | `fetch_traffic_history` | [metrics.md](metrics.md) |
+| [Routing](routing.md) | `fetch_route_table`, `fetch_route_summary`, `fetch_route_lookup` | [routing.md](routing.md) |
 
 ### Universal Dispatch
 
@@ -65,6 +66,7 @@ This endpoint is only available when the server is created with a `NodeProvider`
 | [Уведомления](notice.md) | `fetch_notices` | [notice.md](notice.md) |
 | [Mesh](mesh.md) | `fetch_relay_status` | [mesh.md](mesh.md) |
 | [Метрики](metrics.md) | `fetch_traffic_history` | [metrics.md](metrics.md) |
+| [Маршрутизация](routing.md) | `fetch_route_table`, `fetch_route_summary`, `fetch_route_lookup` | [routing.md](routing.md) |
 
 ### Универсальная диспетчеризация