docs: retire stale Zicbom/VexiiRiscv wording after the OpenC906 swap

The Mini HP core is the locked OpenC906 with T-Head XTheadCmo custom-0
dcache maintenance; the former rv64imafdc_zicbom_max VexiiRiscv
configuration survives only as the frozen Std-series generator asset.
Sweep the leftover wording:

- scripts/README.md gains the missing setup_openc906.py and
  generate_openc906.py entries (locked source install; sha256-pinned
  overrides; single compilation unit below build/).
- configs/README.md and app/README.md describe the OpenC906 core and
  XTheadCmo maintenance instead of VexiiRiscv RTL generation and Zicbom.
- The npu-p5-hp-sim help line and the npu_p5_report.py emitted HP
  evidence mode now say polling-xtheadcmo, matching the payload's
  actual dcache.cva/iva mechanism.

scripts/README.md

@@ -125,6 +125,16 @@ SRAM CoreMark quick report into `meta/coremark.json`; it requires one valid
 `COREMARK_RESULT` record and `COREMARK_PASS`. Both reports complement, rather
 than replace, the common `SIM_TEST_PASS` simulation verdict.
 
+`setup_openc906.py` installs or updates (`--update`) the locked OpenC906
+source used by Mini product profiles and verifies the checked-out revision;
+the vendored checkout is never modified. `generate_openc906.py` resolves the
+upstream `C906_RTL_FACTORY/gen_rtl` filelists from that checkout, substitutes
+the reviewed overrides from `rtl/mini/ip_overrides/` (the hart-1
+`aq_sysio_kid.v` and the strong-order MMIO-window `sysmap.h`, each pinned to
+the upstream file's SHA-256 so a locked-revision move forces review), and
+emits the single compilation unit `openc906_combined.v` below `build/`;
+generated RTL is never tracked.
+
 `generate_vexiiriscv.py` verifies the locked VexiiRiscv revision, rejects local
 source changes before and after generation, and generates the fixed Std-series
 core (preserved from the retired Mini HP configuration) below `build/`; generated

scripts/npu_p5_report.py

@@ -450,7 +450,7 @@ def main() -> int:
                 "softmax_cycles": int(marker.group(4)),
                 **lp_evidence},
             "hp": {"result": str(args.hp_result), "check": str(args.hp_check),
-                "command": hp["command"], "mode": "polling-zicbom",
+                "command": hp["command"], "mode": "polling-xtheadcmo",
                 **hp_evidence},
             "summary": {
                 "required_checks": 47,