Add dedicated --crank monitor for no-start diagnosis

Big ICP readout focused on the cranking scenario:
- Wide ICP bar with the 500-psi firing threshold marked (|)
- Rolling ASCII trace chart of the ICP build-up (10 rows; renders anywhere,
  no unicode) -- clearly shows ICP climbing above/below the 500 firing line
- Peak-hold (the crank's max ICP, the money number) + pass/fail verdict
- FICM main / battery / RPM secondaries with sag (min) tracking
- --dash-log writes a CSV (t,icp,ficm,batt,rpm) while you watch
- On exit prints peak ICP + verdict (reached 500 / suspect oil bleed-off)

Validated end-to-end via a mock crank: ICP ramp past 500, peak capture,
battery-sag capture, trace resolution, CSV logging, clean terminal restore.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

README.md

@@ -32,6 +32,36 @@ python obd_reader.py COM5 --clear   # read, then optionally clear (asks to confi
 python obd_reader.py COM5 -v        # verbose: show raw ELM327 traffic
 ```
 
+### Crank monitor (dedicated no-start view) — `--crank`
+
+The one to use for a crank-but-won't-start. Big ICP readout with a wide bar
+(the `|` marks the 500-psi firing threshold), a **rolling ASCII trace** of the
+ICP build-up, **peak-hold**, FICM/battery/RPM with sag tracking, and a pass/fail
+verdict. Start it, then crank.
+
+```
+python obd_reader.py COM5 --crank                  # crank monitor
+python obd_reader.py COM5 --crank --dash-log crank.csv   # + record a CSV
+```
+
+```
+  ICP  [#################################|##----]   539.8 psi
+  PEAK    540 psi   FIRING PRESSURE REACHED
+  FICM Main 47.5V (min 47.5) [DOC]    Batt 12.6V (min 10.7)    RPM 200
+
+  ICP trace (psi vs time, last 16 samples)
+   600 |
+   500 |----------------------------------------------####   <- firing line
+       |                                            ######
+       |                                          ########
+       +--------------------------------------------------
+```
+
+**Read it:** ICP should climb **past 500 psi within 1–2 s** of cranking
+(`FIRING PRESSURE REACHED`, green). If it **stalls below 500** (red, trace flat
+under the line), that's the high-pressure oil bleed-off — STC fitting / oil-rail
+O-rings. On exit it prints the peak and a verdict. `q` quits, `r` resets.
+
 ### Live dashboard (real-time gauges)
 
 Updates in place as you crank or run the engine — color-coded, with live