Add Companion lost-status replies and repair room mailbox test adapters

Save an opt-in off/no/yes answer to private Am I lost questions from known
chat contacts. Keep reply traffic and ACK state bounded, preserve pending
user delivery, and expose the setting through local CLI and ESP32 WebConfig.

Retain compact STM32 application/filesystem boundaries, qualify the Tag BLE
queue allowance, and exercise saved-image compatibility and browser controls.
Fix stale room mailbox protocol dependencies in the ACL/route test fixtures.

Validation: ten Companion builds, sanitized production-path regressions,
preference fault/compatibility tests, browser tests, and 86 capacity/build
recipe checks passed. No live radio was flashed for this feature.

docs/cli_command_availability.md

@@ -95,6 +95,7 @@ over the normal binary USB, BLE, or TCP connection:
 | [`get public.key`](cli_commands.md#view-this-nodes-public-key) | Companion text terminal and binary command `0x42`; read-only, no private-key export feature required |
 | `get prv.key` | Local terminal and binary command `0x42`; requires private key export enabled |
 | `get password` | Reports that Companion has no admin password; infrastructure returns its password locally |
+| [`get/set lost.reply`](companion_lost_reply.md) | Local Companion CLI and framed command `0x42` when `MESH_ENABLE_LOST_REPLY` is enabled; saved `off`, `no` or `yes` private-message auto response |
 | `get wifi.pwd`, `get mqttN.password`, `get mqttN.token` | Local terminal and binary command `0x42`; corresponding WiFi/MQTT feature required |
 | [`board`](cli_commands.md#show-the-hardware-name) | Every Companion text terminal and command `0x42` |
 | [`version`](cli_commands.md#get-the-version) | Every Companion text terminal and protocol-v14 command `0x42`; returns the untruncated build identity |