docs: reposition as the 86 Panel development environment

The repo's documentation framed it as a support repo for one product
(WardenOS). Since going public the real audience is anyone with a Luckfox
Pico 86 Panel: a maintained 6.18 kernel, an off-device development loop,
and a device simulator that exist nowhere else for this board. Reframe the
README and top-level docs board-first, with WardenOS documented as the
downstream consumer it is (ADR-0008).

Also an editorial pass over the whole doc set:
- every H1/H2 is now a short title, not a sentence (ADRs, qemu/, patches/,
  drivers/, architecture, NPU feasibility, config-lint, payload); workflow
  flowchart titles fixed at the source in tools/flowgen.py and regenerated
  with fresh bench numbers
- README Quick Start commands verified against the scripts; requirements
  corrected (curl, bare python, gcc >= 14) and the MC/DC gate added as a
  step (run green locally on gcc 14.2)
- dropped the 'needs python (not python3)' vendor dig: build-kernel.sh
  inherited the same requirement (filed #10 to remove it)
- glossed MC/DC and HPMCU on first use; marked the tests/uboot-ab
  reference as flare-edge; deduplicated the three-simulator list into the
  root README table

drivers/README.md

@@ -1,11 +1,11 @@
-# drivers/ — our own hardened, hardware-facing drivers
+# Hardened Drivers
 
 Per **ADR-0002** (tiered MC/DC) and **ADR-0005** (source-of-truth), our own
 hardware-facing code migrates here behind a HAL seam and is hardened. "100% MC/DC on
 100% of drivers" is infeasible (≈97% of kernel-driver LOC is vendor blobs — AIC8800
 alone is 88.5K lines); the realistic, honest target is tiered.
 
-## Tier 1 — real 100% MC/DC (here now, CI-enforced)
+## Tier 1 — 100% MC/DC
 
 Self-contained logic with a clean seam, measured to **100% MC/DC** (gcc-14
 `-fcondition-coverage`) by the CI `mcdc` job (`make -C drivers/*/test check`):
@@ -23,7 +23,7 @@ build/test.rc` (it derives the driver name from the `.gcov` file, so there is no
 per-driver copy to keep in sync). The CI `mcdc` job picks up any
 `drivers/*/test/Makefile` automatically.
 
-## Tier 2 — serious testing + fault-injection + benchmarks
+## Tier 2 — Fault Injection
 
 Drivers too large or too vendor/UI-coupled for literal MC/DC get fault-injection,
 branch coverage, and benchmarks against the simulator instead. Their **hardware side