One firmware: the Debug Console in every build, off until switched on, with the device's own token

There is no Debug Build any more (ADR 0010, issue #68, Q188 to Q195). The
console and the test commands are compiled into every firmware. It listens
only while Settings > Debug Console is on, which isn't the default; off,
neither its task nor its 4 KB ring exists. The token is made by the device
and shown on that page; a client proves it knows it by answering a challenge
with an HMAC, so it never crosses the network, and five wrong answers close
the console for a minute. DBG in the Status Bar while it listens.

Over USB serial only: debug on, debug token <value>, debug token new.
scripts/flash.sh --debug uses them to set a device up with the developer's
token. scripts/rdbg.py takes the token from -t, $RORO_DEBUG_TOKEN or the
file, answers the challenge, and fetches a release's ELF to decode a crash.

Gone: the cardputer-adv-debug environment, RORO_DEBUG, the +debug version,
scripts/debug_flags.py, update install ... force, and the rule that a Debug
Build doesn't install releases. Old clients and old firmwares don't talk to
each other.

Against the builds it replaces: 30 KB more flash and 88 bytes more static
RAM than the release, 4 KB less RAM than the Debug Build. 468 host tests.
Checked on the device: off by default, login, the pause after wrong tokens,
Safe Mode with the console, the setting surviving an update, debug off.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

lib/services/src/settings.cpp

@@ -1,5 +1,6 @@
 #include "settings.h"
 
+#include "debug_auth.h"
 #include "ipv4.h"
 
 namespace roro {
@@ -41,6 +42,8 @@ const Definition kDefinitions[] = {
     {"ntp2", Kind::String, 0, "time.cloudflare.com", 0, 63},
     {"gnss_quiet", Kind::Bool, 0, nullptr, 0, 1},  // off: GNSS stays on, as decided in M2 (Q58)
     {"check_updates", Kind::Bool, 1, nullptr, 0, 1},  // on: it only looks, and says so (R1, Q165)
+    {"debug_on", Kind::Bool, 0, nullptr, 0, 1},  // off: nothing listens until the owner says so (Q189)
+    {"debug_token", Kind::String, 0, "", 0, 64},  // empty, or a valid token
 };
 static_assert(sizeof(kDefinitions) / sizeof(kDefinitions[0]) == static_cast<size_t>(Setting::Count),
               "every Setting needs a definition");
@@ -98,6 +101,7 @@ bool Settings::validString(Setting s, const std::string& value) const {
     if (s == Setting::Dns2) return value.empty() || net::parseIpv4(value, address);
     if (s == Setting::Ntp1) return net::validHost(value);
     if (s == Setting::Ntp2) return value.empty() || net::validHost(value);
+    if (s == Setting::DebugToken) return value.empty() || debug::validToken(value);
     return true;
 }
 

lib/services/src/settings.h

@@ -31,6 +31,8 @@ enum class Setting : uint8_t {
     Ntp2,             // string: the second, or empty
     GnssQuietForLora, // bool: put the GNSS receiver in standby while the LoRa radio listens (issue #20)
     CheckUpdates,     // bool: look for a newer release on Gitea once a day (R1, Q165)
+    DebugConsole,     // bool: the Debug Console listens on Wi-Fi (ADR 0010, Q189: off unless switched on)
+    DebugToken,       // string: its token, tidied (debug_auth.h); empty until the console is first switched on
     Count
 };