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  ADR-0004 marked superseded-in-part; docs/ci-cd.md rewritten (site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

drivers/README.md

@@ -38,7 +38,7 @@ is already modelled and tested here** in `../sim/`:
 **Why the Tier-2 *source* isn't vendored here yet:** `modbus_engine.c` and
 `warden_rga.c` pull in shared UI headers (`platform.h`, `settings.h`, `lv_*`) and
 librga. Copying those in would duplicate exactly the shared surface the
-**flare-edge↔warden-sdk unification** (ADR-0003/0005, a separate [maintainer]-gated step) is
+**flare-edge↔warden-sdk unification** (ADR-0003/0005, a separate maintainer-gated step) is
 meant to resolve cleanly. So the Tier-2 *models* (the hardware ends) live here now;
 the Tier-2 *driver sources* migrate in with the unification, at which point their
 existing flare-edge harnesses point at this repo.

drivers/enforce-mcdc.sh

@@ -52,5 +52,5 @@ if ! echo "$cond_line" | grep -q "100.00%"; then
 	rc=1
 fi
 
-[ "$rc" = "0" ] && echo "RESULT: 100% MC/DC + all checks green ✓"
+[ "$rc" = "0" ] && echo "RESULT: 100% MC/DC + all checks green OK"
 exit "$rc"