Add mqttstats: headless Commodity for Home Assistant telemetry - #22

A standalone AmigaOS Commodity publishing Amiga system telemetry
(uptime, chip/fast RAM free, CPU model) to a Home Assistant broker via
mqtt.library, with full MQTT Discovery so sensors appear automatically.
Configured entirely through Workbench ToolTypes (via amiga.lib's
ArgArrayInit), runnable silently from WBStartup, with Commodities
Exchange as its only control surface (Enable/Disable/Kill) - the
telemetry piece of issue #6, scoped ahead of I2C sensor support which
remains a follow-up.

Adds the portable src/tools/ha_discovery.[ch] module (HA MQTT Discovery
topic/payload builder, host-unit-tested) shared with mqttstats, and
userdocs/mqttstats.md covering ToolTypes and Home Assistant setup.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QWq1CRLCQy9AaD9UtLRSM9

Without a .info icon, mqttstats couldn't actually be double-clicked or
dropped into WBStartup: - a direct requirement from the issue this
tool was built for. tools/mkicons.py (ported from AmiAuth's generator)
produces a classic 4-colour, 2-bitplane DiskObject icon with a few
common Tool Types pre-listed as edit-in-place comments (HOST,
CLIENTID, INTERVAL, CX_PRIORITY).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QWq1CRLCQy9AaD9UtLRSM9

… version sensors

- Icon now lists every ToolType (not just four), all disabled/commented -
  matches every read_config() key so nothing is hidden from the icon.
- Initial MQTT_Connect() failures now retry with capped exponential
  backoff (mco_AutoReconnect only covers post-connect drops, not a failed
  first attempt) - lets mqttstats launch from WBStartup ahead of the
  TCP/IP stack's own startup entry without just quitting once.
- Added MQTT_CONNECT_REFUSED (-102) as a proper public constant in
  mqtt.library's <libraries/mqtt.h> (mqtt.doc updated, api-reference
  regenerated). mqttstats checks for it specifically: unlike a transient
  connect failure, a CONNACK refusal (bad credentials, rejected client
  id, ...) means retrying won't help, so it opens intuition.library
  itself and shows a one-off EasyRequest before quitting - mqtt.library
  itself stays UI-free, this is purely the caller's own choice.
- Added Kickstart version and Workbench version telemetry sensors
  (exec.library's and workbench.library's own lib_Version/lib_Revision).
  Formatting them hit a confirmed m68k-amigaos-gcc -O2 miscompile
  (garbage upper bits when a UWORD struct field reaches sprintf's "%u"
  varargs); worked around with a dedicated noinline manual formatter -
  see format_bcd_version()'s own comment for the full story.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QWq1CRLCQy9AaD9UtLRSM9

TR_GETSYSTIME doesn't measure time since reset - it returns the same
absolute, calendar-rooted system clock DateStamp() is built on (seconds
since 1978-01-01, set from the battery-backed RTC at boot), just with
sub-second precision. Reported as "uptime" it produced a nonsensical
~48-year value on any machine with a working clock - caught in real use.

Switched to ReadEClock()'s free-running hardware tick counter, which
genuinely resets to 0 at power-on and has no notion of calendar date at
all, while remaining exactly as immune to the DateStamp() clock-jump
hazard issue #8 documents.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QWq1CRLCQy9AaD9UtLRSM9

… it mid-word

Exchange's list truncates nb_Descr on OS 3.1 well before the end,
cutting "...to Home Assistant via MQTT" down to "...to Home Ass".
Reordered so "Home Assistant" lands safely inside the observed
~37-character cutoff instead of running off the end of the string.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QWq1CRLCQy9AaD9UtLRSM9