Correct the camera triage: both Pi 5 connectors take a camera

The first version told the reader a camera in "a DISP port" would never appear.
That is Pi 4 thinking. The Pi 5 has two 4-lane MIPI connectors, CAM/DISP 0 and
CAM/DISP 1, and BOTH are dual-purpose — either one accepts a camera. Left as
written it would have sent someone hunting a port mix-up that cannot happen,
and away from the likelier cause.

Promotes that likelier cause to the top: the Pi 5 uses the narrow 22-pin FPC,
while Pi 4-era camera modules ship with a 15-pin cable and need the adapter.

Also records the evidence that narrows this to hardware rather than config.
pisp_be is loaded and /dev/media0-2 exist, so the imaging pipeline is up, but
/sys/bus/i2c/devices holds only i2c-13 and i2c-14 — no camera bus was
instantiated and no CFE bound. camera_auto_detect probes at boot and loads a
sensor overlay when it finds one, so an absent bus means the firmware found
nothing to probe. Confirmed unchanged across a reboot.

README.md

@@ -30,21 +30,38 @@ This is a *detection* problem, not a software one — the userland is already in
 - **`dmesg` contains no camera probe lines at all** — no sensor (`imx*`, `ov5647`), no CFE
 
 That last point is the diagnostic one. A camera that is seen but misconfigured still leaves probe
-messages; **silence means the sensor is not being reached electrically.** So check the physical
-connection before changing any config:
+messages; **silence means the sensor is not being reached electrically.**
 
-1. The Pi 5 has **two CAM/DISP connectors, and they are interchangeable in shape** — a camera in a
-   DISP port looks correctly seated and will never appear.
-2. Ribbon **orientation**: contacts face the correct side at both ends (the board end and the camera
-   end are not the same way round).
+The imaging pipeline itself is fine, which narrows it further:
+
+```console
+$ lsmod | grep -iE 'pisp|cfe'
+pisp_be                49152  0          # ISP backend loaded
+$ ls /sys/bus/i2c/devices/
+i2c-13  i2c-14                           # no camera i2c bus
+```
+
+`camera_auto_detect=1` probes the connectors at boot and loads a sensor overlay when it finds
+something. **No sensor i2c bus was instantiated and no CFE bound**, so the firmware found nothing to
+load an overlay for. Nothing in software will change that.
+
+So check the physical connection, power off first:
+
+1. The Pi 5 uses the **narrower 22-pin** FPC connector. Cameras from the Pi 4 era ship with a
+   **15-pin** cable, which needs the 22-pin-to-15-pin adapter cable — this is the most common cause
+   of a camera that is connected but invisible.
+2. Ribbon **orientation**: contacts face the correct side at *each* end, and the two ends are not the
+   same way round.
 3. The connector latch is fully seated at both ends.
-4. The Pi 5 uses the **narrower 22-pin** connector — a 15-pin camera cable needs an adapter.
+4. Try the **other connector** — the Pi 5 has two, `CAM/DISP 0` and `CAM/DISP 1`, and **both are
+   dual-purpose**, so either accepts a camera. Swapping isolates a faulty port.
 
-Power off before reseating. Re-check with:
+Re-check with:
 
 ```bash
-rpicam-hello --list-cameras     # should list a sensor
-dmesg | grep -iE 'imx|ov5647|cfe'
+rpicam-hello --list-cameras          # should list a sensor
+dmesg | grep -iE 'imx|ov5647|cfe'    # should show a probe
+ls /sys/bus/i2c/devices/             # a new bus should appear
 ```
 
 ⚠ **Do not treat `/dev/video*` as evidence the camera works.** Those nodes exist on this Pi already