diagnostics: confirm ICP bleed-off via --crank (peak 376 psi)

Direct on-truck measurement with the verified 1446 ICP PID: peak
cranking ICP 376 psi vs the ~500 psi firing threshold.  FICM Main min
48.0 V (healthy), battery min 10.3 V (adequate).  Diagnosis empirically
confirmed: high-pressure oil bleeds off during cranking.  376 psi is
"almost there" not zero, which fits a partial leak (IPR seat / oil rail
O-rings / partial STC crack) rather than a fully blown STC fitting.

- Capture the --crank output in crank-test-2026-06-30.txt
- Add EMPIRICAL CONFIRMATION section to diagnostics README
- Update handoff "resume at the truck" to lead with physical inspection
  (IPR -> STC -> oil rail O-rings), since the OBD-side diagnosis is done

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

diagnostics/2026-06-29-no-start/README.md

@@ -38,6 +38,24 @@ No engine P-codes, no FICM codes, no injector codes, no CMP/CKP codes.
   injector drive, cam/crank sync, and the FICM-to-injector path are all
   good when the engine is turning at running RPM.
 
+## ⭐ EMPIRICAL CONFIRMATION (2026-06-30 crank test)
+
+Direct measurement with `--crank` and the verified `1446` ICP PID:
+
+**Peak cranking ICP = 376 psi** — below the ~500 psi firing threshold.
+Full output in [crank-test-2026-06-30.txt](crank-test-2026-06-30.txt).
+
+This is the smoking gun. Truck cannot generate enough ICP during cranking
+to open injectors → cannot fire on its own fuel → needs ether every time.
+Matches the symptom-set perfectly.
+
+Side data from the same test:
+- **FICM Main min: 48.0 V** — healthy, corroborates the meter.
+- **Battery min: 10.3 V** — sag but adequate.
+- 376 psi is "almost there" not zero → suggests a **partial** leak
+  (IPR seat / oil rail O-rings / partial STC crack) rather than a
+  fully blown STC fitting (which would typically show sub-100 psi).
+
 ## ⭐ Key diagnostic finding: ether starts it every time
 
 Spraying starting fluid (ether) into the intake **gets the truck to fire,