public-readiness: scrub internal details, split licensing, hosted kernel-build

Preparing the repo to go public (ADR-0007):

- CI: kernel-build moves from the self-hosted runner to ubuntu-latest
  (installs its own cross toolchain + qemu, caches the pristine tarball).
  On a public repo a registered self-hosted runner is reachable from
  approved fork-PR workflows — i.e. arbitrary code on private
  infrastructure — and the build never actually needed the SDK host.
  ADR-0004 marked superseded-in-part; docs/ci-cd.md rewritten (site
  specifics now live only in the private deployment log).
- Licensing: LICENSE gains the GPL-2.0 carve-out for patches/ and the
  kernel source excerpts (Linux derivatives; per-driver provenance was
  already tracked in PROVENANCE.md); patches/README.md states it too.
- Scrubbed from the tip: bench-unit dev credentials and its gadget IP
  (m2-boot notes), the site AP SSID+BSSID and a neighboring AP's BSSID
  and the device WLAN MAC (wifi bring-up evidence — BSSIDs are
  geolocatable), the runner mesh IP. NOTE: these remain in git history;
  decision on a pre-publication history rewrite is separate.
- Emoji cleanup across 21 tracked files (kernel port docs, review report,
  enforce-mcdc.sh) per repo text conventions: status marks became
  [x]/[wip]/[ ]/OK plain text.
- "[maintainer]-gated" process phrasing normalized to "maintainer-gated"
  (attributions in dated evidence docs kept).

Verified: zero emojis tracked; scrub grep clean; patches carry no internal
references; ci.yml parses; shellcheck unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018HUayid7W5w7jBdb9Rrj1K

patches/README.md

@@ -27,6 +27,14 @@ with `../build/warden_defconfig` → `zImage` + `rv1106-warden.dtb`).
 | `70-audio-codec.patch` | `rv1106_codec` + I2S wiring |
 | `80-misc-thermal-rtc-adc.patch` | tsadc, rtc-rockchip, saradc, trng, otp, gmac, goodix touch |
 
+## License
+
+Everything in this directory is a derivative work of the Linux kernel and of
+GPL-2.0 vendor kernel code: **GPL-2.0-only** (or the per-file SPDX identifier
+where one is present), regardless of the MIT/Apache dual license the rest of
+the repository uses. See the top-level `LICENSE` and
+`kernel/rv1106-enablement/PROVENANCE.md` (per-driver origin + license).
+
 ## Provenance & regeneration
 
 Baseline: `linux-6.18.46` from kernel.org (`build/linux-6.18.46.tar.xz.sha256`