docs(webcam): tuning tools in the app-suite template + libcamera gap filed

- templates/downstream/home.nix: commented "Webcam tuning" entries
  (cameractrls, v4l-utils) — bare packages, so template not toggle,
  per the option-surface rule; rarely needed since the IR-hide covers
  the common dual-sensor case.
- agent/BACKLOG.md PROPOSED: the portal/Flatpak camera picker still
  lists the internal IR sensor (libcamera path, untouched by the v4l2
  rule) — three options laid out, recommending document-only until a
  T14s-style machine is available to test a libcamera-side rule.

Closes BACKLOG NOW#7. Verified: V0 (flake check green; template still
evaluates through mkFlake).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

agent/JOURNAL.md

@@ -17,6 +17,19 @@ Template:
 
 ---
 
+## 2026-07-04 — Webcam follow-ups (loop iteration #5, quick item)
+- **Task:** BACKLOG NOW#7 (Bernardo asked for "a quick item").
+- **Did:** template `home.packages` gains a commented "Webcam tuning"
+  pair (cameractrls GUI, v4l-utils CLI — bare packages, so template not
+  toggle, per the option-surface rule); the portal/Flatpak libcamera IR
+  gap is written up as a PROPOSED item with three options (recommend:
+  document-only now, libcamera-rule investigation when the T14s is
+  available). CI runs #60/#61 confirmed green (earlyoom + snapshot fix).
+- **Verified:** V0 (flake check — template evals through mkFlake;
+  changes are comments + agent docs).
+- **Next suggestion:** NOW#5 (keyboard cycle bind + summer parity) —
+  the last code item in NOW besides the docs pass.
+
 ## 2026-07-04 — Snapshot GUI un-broken + polkit agent (loop iteration #4)
 - **Task:** BACKLOG NOW#4 — btrfs-assistant segfault.
 - **Did:** re-diagnosed instead of overriding. gdb: crash is in