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

docs/workflows/README.md

@@ -1,11 +1,11 @@
-# Workflow flowcharts
+# Workflow Flowcharts
 
 Generated by `tools/flowgen.py` from the modelled decision paths.
 Each is an outcome-first flowchart of a workflow the SDK tests, with its benchmark or MC/DC metric.
 
-- [HPMCU watchdog: arm → beat → fire](hpmcu-watchdog.md)
-- [Modbus RTU: read-holding-registers round trip](modbus-read-holding.md)
-- [CRU reset ladder: cause + boot-mode survival](cru-reset-ladder.md)
-- [RGA 2D offload dispatch](rga-offload.md)
-- [Relay drive (Tier-1, 100% MC/DC)](relay-drive.md)
-- [UI freshness contract (Tier-1, 100% MC/DC)](freshness-contract.md)
+- [HPMCU Watchdog](hpmcu-watchdog.md)
+- [Modbus RTU Round Trip](modbus-read-holding.md)
+- [CRU Reset Ladder](cru-reset-ladder.md)
+- [RGA Offload](rga-offload.md)
+- [Relay Drive](relay-drive.md)
+- [UI Freshness Contract](freshness-contract.md)