fresnel-fourier iter1 Phase 6 commit D: drop missed mpeg2-ctrls.h include from context.c

Fix-forward for commit C (3aab187): Phase 2 source-read missed a
third occurrence of #include <mpeg2-ctrls.h> in src/context.c:42.
The Phase 2 grep audit reported only two callsites
(src/config.c:37, src/mpeg2.c:38), both removed in commit B.
After commit C deleted include/mpeg2-ctrls.h from disk, the build
broke on context.c with:

  ../src/context.c:42:10: fatal error: mpeg2-ctrls.h:
  No such file or directory
     42 | #include <mpeg2-ctrls.h>
        |          ^~~~~~~~~~~~~~~

The include in context.c was vestigial — context.c references no
V4L2_CID_MPEG_VIDEO_MPEG2_* symbols and never needed the header
even before iter1's rewrite. The Phase 2 grep was simply incomplete.

This commit drops the orphan include line. Build now passes; install
clean; Phase 1 criterion 4 (DMA-BUF GL HW=SW byte-identical pixel
hashes) still PASS:

  HW frame 1: 6e7873030dbf0403c67f35dd106ebef3c7909a0fd12433b82ad758e7fee9f092
  SW frame 1: 6e7873030dbf0403c67f35dd106ebef3c7909a0fd12433b82ad758e7fee9f092
  HW frame 2: ccc7ce08810d4a96e9ba7a19f4f95bbf6cc861bda9337604b5c668ad52bef7de
  SW frame 2: ccc7ce08810d4a96e9ba7a19f4f95bbf6cc861bda9337604b5c668ad52bef7de

Per feedback_dev_process.md Phase 6 discipline:
"If a plan revision is needed mid-implementation, surface it
explicitly and re-enter Phase 4."

This is a 1-line scope expansion of commit B's "drop mpeg2-ctrls.h
include from all callsites" intent. Surfacing explicitly here
rather than silently amending B (which is already pushed). No
re-lock of plan needed; the spirit of File 1+2 in
phase4_iter1_plan.md was "drop the include from every file that
has it." The audit method (Phase 2 grep) was the gap.

Lesson for Phase 8 memory update: a more authoritative completeness
check than naive grep before deleting a header — recursive build
attempt to drive out hidden includes, or grep with no path filter
would have caught it.

Refs:
  ../fresnel-fourier/phase4_iter1_plan.md (File 3 + audit)
  ../fresnel-fourier/phase2_iter1_situation.md Bug 3 (incomplete
                                                     audit)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/context.c

@@ -39,7 +39,6 @@
 
 #include <linux/videodev2.h>
 
-#include <mpeg2-ctrls.h>
 #include <hevc-ctrls.h>
 
 #include "utils.h"