fix(code-runtime-python): correct the log-budget floor to 64 and record the marker envelope bound

The review found the 62 floor off by two (the marker's fixed prefix is 51
characters counting both square brackets, so marker(62) serializes to 63) and
the constructor error over-claiming a bound the marker-as-envelope design does
not deliver. Fixes:
- MIN_LOG_BYTES is 64 (marker-only serialization fits with one byte of room);
  the JSDoc arithmetic counts the brackets; the rejection test pins 63; the
  forged-frame test uses 11 NULs (69 escaped) at 64.
- The constructor error now states the marker-only guarantee, and the README
  Known Limitations (en + zh) records the real bound: a truncated run with
  admitted entries serializes its logs to maxLogBytes + marker + envelope.
- The SIGXCPU-mask tests burn with time.process_time() instead of wall-clock
  perf_counter, so a contended CI runner cannot under-burn the budget.
- The settlement note (en + zh) records the 64 floor and the marker envelope
  bound, including the zh pre-encode section that the earlier pass missed.
- The README constructor-rejection list names the maxLogBytes floor.
Pairings re-recorded; corpus-wide verify-translation-pairing passes 1004.

packages/code-runtime/code-runtime-python/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/code-runtime/code-runtime-python/README.md
-README.md: 18c784394705e7fc10f956bcbf7e576d6a0b4c83
-README.zh.md: 64424b7d2de8b96452469c3e65e47ed3d9a91adb
+README.md: 25211993e1ebac7b940d4f373391819c15cab5c0
+README.zh.md: ca260b8c8d543545ce927f2c48e4676b34622786