exthost.service: a package's frame with the lamp named

The reference service takes two more lid-camera frames through its API
socket, with the camera's lamp at 0 and at 1023, and one with a lamp
past its range. The test holds both named frames to being JPEGs, the lit
one the larger (the lamp reached the camera and changed the picture),
and the out-of-range one to a 400 that names the lamp. The service's
text is shared by every exthost test, and every one of them already
covers forgeext's api.c and run.c, which this change moves, so no test
is made stale that was not stale already.

Proof: on the bench reference, image 20260922225653 with forgeext
cd8b471b and forgectrl 9c9ee557 bind-mounted, exthost.platform and
exthost.service PASS: 51,561 bytes at lamp 0, 109,850 at lamp 1023,
and lamp 5000 refused.

forgetest/forgetest/suite/exthost.py

@@ -616,6 +616,9 @@ report = {
     "api_camera": shot({"camera": "lid", "resolution": "half"}),
     "api_camera_head": shot({"camera": "head"}),
     "api_camera_bad": shot({"camera": "bed"}),
+    "api_camera_dark": shot({"camera": "lid", "resolution": "half", "lamp": 0}),
+    "api_camera_lit": shot({"camera": "lid", "resolution": "half", "lamp": 1023}),
+    "api_camera_lamp_bad": shot({"camera": "lid", "lamp": 5000}),
     "api_settings": api("GET", "/v0/settings"),
     "api_settings_set": api("POST", "/v0/settings", {"threshold": 70, "note": "set from inside"}),
     "api_settings_undeclared": api("POST", "/v0/settings", {"nothere": 1}),
@@ -897,7 +900,9 @@ def _as_found(ctx, fc, prior, raw, dir_mode, found_tree):
                   "address even on the port it declared, cannot connect on a port it did not declare, and "
                   "cannot open a netlink socket. Its one way to the machine is its API socket (root's and its "
                   "account's, 0660, refused to another pool account): GET /v0/self names it and what it may use, "
-                  "GET /v0/machine/mode is forgectrl's answer relayed, a hold it was not granted is 403, a path "
+                  "GET /v0/machine/mode is forgectrl's answer relayed, POST /v0/camera gives it a JPEG from the "
+                  "lid camera it holds (with the camera's lamp at 0 and at 1023 two different pictures, the lit "
+                  "one the larger) and refuses the head camera and a lamp past its range, a hold it was not granted is 403, a path "
                   "the API does not have 404, a path with .. 400; its output is in the forgeext log under its id. Safe mode "
                   "stops it and its end starts it again. A host killed outright takes its services with it "
                   "at once (the init wrapper), comes back, and starts the service again. ext_enabled=0 "
@@ -1034,6 +1039,22 @@ def service(ctx):
         badcam = rep.get("api_camera_bad") or [0, ""]
         ev["api_camera_bad"] = badcam[:2]
         ctx.check(badcam[0] == 400, "a camera there is none of -> %s", badcam[:2])
+        # The camera's own lamp for one frame: the machine lights it for
+        # the shot and puts its level back, so a frame with the lamp off
+        # and one with it full are two different pictures, the lit one the
+        # larger, and a level past the range is refused before the machine
+        # is asked.
+        dark = rep.get("api_camera_dark") or [0, "", False, False]
+        lit = rep.get("api_camera_lit") or [0, "", False, False]
+        ev["api_camera_lamp"] = {"dark": dark[:3], "lit": lit[:3]}
+        ctx.log("the lid camera with its lamp at 0 and at 1023: %s", ev["api_camera_lamp"])
+        ctx.check(dark[0] == 200 and dark[2] and lit[0] == 200 and lit[2],
+                  "a frame with the lamp named did not come back as a JPEG: %s", ev["api_camera_lamp"])
+        ctx.check(isinstance(lit[1], int) and isinstance(dark[1], int) and lit[1] > dark[1],
+                  "the lamp did not reach the camera: %d bytes at 1023, %d at 0", lit[1] or 0, dark[1] or 0)
+        lampbad = rep.get("api_camera_lamp_bad") or [0, ""]
+        ev["api_camera_lamp_bad"] = lampbad[:2]
+        ctx.check(lampbad[0] == 400 and "lamp" in str(lampbad[1]), "a lamp past its range -> %s", lampbad[:2])
 
         # A package's capture yields to somebody watching a camera: it is
         # never the person standing at the machine.