VIDIOC_STREAMON returns EPIPE on Meteor Lake (Surface Pro 10) with OV13858 sensor

**Hardware:** Microsoft Surface Pro 10
**SoC:** Intel Core Ultra (Meteor Lake)
**IPU:** Intel IPU6 [8086:7d19] rev 04
**Kernel:** 6.18.7-surface-1
**Firmware present:** /lib/firmware/intel/ipu/ipu6epmtl_fw.bin.zst

**Sensor detected:**
- ov13858 on /dev/v4l-subdev6
- Connected to Intel IPU6 CSI2 0 via ENABLED,IMMUTABLE link
- Sensor controls fully responding (exposure, gain, orientation shows "Back")
- pixel_rate: 432000000, link_frequency: 540000000

**Steps to reproduce:**
media-ctl -l '"Intel IPU6 CSI2 0":1 -> "Intel IPU6 ISYS Capture 0":0 [1]'
media-ctl -V '"Intel IPU6 CSI2 0":0 [fmt:SGRBG10_1X10/4224x3136 field:none]'
media-ctl -V '"Intel IPU6 CSI2 0":1 [fmt:SGRBG10_1X10/4224x3136 field:none]'
v4l2-ctl -d /dev/video0 --set-fmt-video=width=4224,height=3136,pixelformat=BG10
v4l2-ctl -d /dev/video0 --stream-mmap --stream-count=1 --stream-to=/tmp/test.raw --verbose

**Result:**
All VIDIOC calls succeed (REQBUFS, QUERYBUF, QBUF) but
VIDIOC_STREAMON returned -1 (Broken pipe)
Zero kernel log output during failure - no error from firmware layer.

**Expected:** Frames captured to file

**Notes:**
- ipu6-camera-bins directory present with full library/include tree
- No IPA found warning from libcamera (No IPA in /usr/lib/x86_64-linux-gnu/libcamera)
- media-ctl topology shows 48 capture nodes across 6 CSI2 controllers
- Pipeline configuration accepted without errors