sd card: what the card says it is, from its CID register

Type, size, and the identity register read by our SD driver (CMD10):
manufacturer, OEM, product name, revision, serial and date, decoded by a
host-tested parser. Needed for the upstream report of #21: nothing else
here could read the card's identity. This one is a Samsung 8 GB SDHC
from June 2013.

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

README.md

@@ -76,6 +76,7 @@ The LoRa Scanner (docs/milestones/M3.md) listens with the Cap's radio and **neve
 | `short` / `normal` | Screen timeouts 5 s / 10 s, or 30 s / 60 s |
 | `wifi add <ssid><TAB><password>` | Adds a Saved Network (so credentials stay out of the repo) |
 | `log <text>` | Appends a line to a test IRC Log (`/irc/dev/#test/<date>.log`) |
+| `sd card` | What the SD card says it is: type, size, and its identity register (maker, name, revision, serial, date) |
 | `sd list` | Lists the files of each Storage Clean-up category |
 | `cat <path>` | Prints the first ~1.2 KB of a file on the SD card |
 | `irc start` | Starts the IRC Service (normally done by opening the IRC App) |