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

scripts/debug_flags.py

@@ -1,12 +0,0 @@
-# Debug Builds only: compiles in the Debug Console token from $RORO_DEBUG_TOKEN (set by _docker.sh
-# from ~/.config/roro9stack/debug-token). Refuses to build without one rather than use a default.
-import os
-import re
-import sys
-
-Import("env")  # noqa: F821  (provided by PlatformIO)
-
-token = os.environ.get("RORO_DEBUG_TOKEN", "").strip()
-if not re.fullmatch(r"[0-9a-f]{32}", token):
-    sys.exit("debug build: RORO_DEBUG_TOKEN is missing; build through scripts/ci.sh or scripts/flash.sh --debug")
-env.Append(CPPDEFINES=[("RORO_DEBUG_TOKEN", '\\"%s\\"' % token)])  # noqa: F821