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  ADR-0004 marked superseded-in-part; docs/ci-cd.md rewritten (site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

docs/decisions/0005-driver-source-of-truth.md

@@ -12,7 +12,7 @@ scratch tree (`flare-edge/research/linux-6.18.46/`).
 Bring **hardened copies into `warden-sdk/drivers/`** as the canonical source-of-truth,
 each with its HAL seam and a 100% MC/DC host harness. The RV1106 kernel deltas are
 formalized as a patch series in `patches/`. flare-edge consumes warden-sdk later
-(separate, [maintainer]-gated step).
+(separate, maintainer-gated step).
 
 ## Consequences
 - Realizes the seam architecture (ADR-referenced in `docs/architecture.md`).