docs(weather-mesh): record 042 OSS implementation status + mesh-mode usage

Plan 042 status now reflects the implemented OSS work packages (WP1, WP3's
043 doc, WP4, WP5, WP6 and the verification follow-ups); the demo README
documents the opt-in public-mesh mode (MESH_SLOTS/MQTT_URL/AIMX_BIND, the
weather-station join loop, gamma's MESH_CONFIG build embedding) alongside
the unchanged local demo.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: lxsaah

docs/plan/042-public-weather-mesh-flagship.md

@@ -2,7 +2,7 @@
 
 **Design:** [042 — Public weather mesh flagship](../design/042-public-weather-mesh-flagship.md)
 
-**Status:** 📝 Planned
+**Status:** 🚧 OSS work packages implemented 2026-07-09 (WP1, WP3's 043 doc, WP4, WP5, WP6 — plus the mqtts:// TLS-transport fix in the Tokio MQTT client the WP1 premise relied on, a read-only AimX TCP endpoint in the hub's mesh mode so the §7 `aimdb record list` loop has a server, and CLI observability metadata so signal gauges round-trip). External WPs (WP2 broker, WP3 provisioning service, WP8 website) and WP7 (Embassy TLS) remain open.
 
 This plan translates the design's sequencing (§10) into concrete work packages
 (WPs). Each WP is marked by where the work happens:

examples/weather-mesh-demo/README.md

@@ -27,6 +27,7 @@ A distributed weather monitoring mesh demonstrating AimDB's multi-tier architect
 | `weather-station-alpha` | Tokio (Linux Edge) | Real weather data (Open-Meteo API) |
 | `weather-station-beta` | Tokio (Linux Edge) | Synthetic sensor data |
 | `weather-station-gamma` | Embassy (STM32H563ZITx) | Portable/remote MCU sensor (hardware) |
+| `weather-station` | Tokio (anywhere) | Public-mesh station, driven by a `station.toml` profile |
 | `weather-mesh-common` | no_std compatible | Shared contracts and configuration |
 | `mqtt` | Eclipse Mosquitto | Message bus for all nodes |
 
@@ -110,6 +111,33 @@ cargo build --release
 probe-rs run --chip STM32H563ZITx target/thumbv8m.main-none-eabihf/release/weather-station-gamma
 ```
 
+## Public mesh mode (design 042)
+
+The same crates also run the hosted public mesh anyone can join
+([design 042](../../docs/design/042-public-weather-mesh-flagship.md)). The
+local demo above is unchanged; mesh mode is opt-in per environment variable:
+
+- **Hub** — `MESH_SLOTS=64 cargo run -p weather-hub` replaces the three-enum
+  configuration with a bounded pool of string-keyed slot records
+  (`station.{slot}.temperature/humidity/dew_point` from
+  `station/{slot}/…` topics; dew point derived at the hub). `MQTT_URL` takes
+  a full connector URL (e.g. `mqtts://hub-sub:…@…:8883` for EMQX Cloud), and
+  a read-only AimX endpoint is served at `AIMX_BIND`
+  (default `127.0.0.1:7433`) for `aimdb record list/get/watch`.
+- **Station** — the three-command join loop
+  ([format doc 043](../../docs/design/043-join-endpoint-v1.md)):
+
+  ```bash
+  aimdb join https://mesh.aimdb.dev          # writes station.toml
+  cargo run -p weather-station -- --config station.toml
+  aimdb record list --connect tcp://aimdb.dev:7433
+  ```
+
+- **MCU station** — same profile, consumed at build time:
+  `MESH_CONFIG=../station.toml cargo run --release` inside
+  `weather-station-gamma` (plain-TCP brokers only until the Embassy MQTT
+  client speaks TLS — design 042 §8.1).
+
 ## Inspecting with VS Code Copilot
 
 The weather mesh exposes an AimX API socket that Copilot can read through MCP (Model Context Protocol). Simply ask Copilot in natural language: