build(vivado): rewrite create_project.tcl for current KeyGen flow

The old script referenced 5 non-existent files (keccak_arbiter,
sha3_chain_top_shared, tb_mlkem_top_xsim, tb_kg/en/de) and stale
vectors, so read_verilog/elaborate failed outright.

Rewrite to mirror the verified XSIM flow (sync_rtl/top/TB/xsim_run.tcl):
  - load exactly the 14 sources mlkem_top depends on
  - sim top = tb_mlkem_kg_katK_xsim, runtime K via generic KP, case via
    -testplusarg CASE
  - copy KAT vectors into the xsim working dir via xsim.compile.tcl.pre
    (the only hook in 2019.2 that runs before $readmemh; an appended
    -tclbatch runs after Vivado's own 'run all', too late)
  - drop duplicate --relax (XSim adds it; passing again is an error)

Verified through the actual Vivado batch project flow:
  K=2 CASE 0 -> PASS (21403 cyc), K=4 CASE 2 -> PASS (54059 cyc),
  0 file-not-found warnings. gitignore the generated vivado_prj/.

Also rewrite README.md in Chinese documenting the mlkem_top workflow
and test flow.

.gitignore

@@ -33,3 +33,6 @@ Thumbs.db
 
 # Session runtime continuation cache
 .omo/
+
+# Generated Vivado project (create_project.tcl)
+vivado_prj/