fix(log): prevent formatter size wrap

[Zartharas]

Summary

Prevent m1_logdb_dyn_vsprintf() from truncating the dynamic buffer size through an 8-bit uint8_t temporary.

For certain oversized formatted outputs, ret_n + 20 can exceed 255 and wrap back below the formatter's size cap. A 240-byte formatted result reproduces the repeated state deterministically: 240 + 20 -> 260 -> 4, after which the formatter can repeat the same allocation/format cycle.

The fix is intentionally minimal:

- uint8_t mem_size;
+ int mem_size;

Validation

• Independent host reproduction of the upstream size-wrap/repeated-state defect: PASS
• Corrected host behavior: PASS
• Paired ARM baseline/fixed builds with Arm GNU 14.2.Rel1: PASS
• Baseline warnings: 1076
• Fixed warnings: 1076 (warning_delta=0)
• Baseline/fixed build errors: 0
• Firmware artifact size delta: 0 bytes for BIN, CRC BIN, ELF, and HEX
• ELF memory footprint delta: text=0, data=0, bss=0
• Cold-rebuilt baseline reproduced the historical WP1 firmware artifacts byte-for-byte
• Fixed firmware rebuilt twice with byte-identical BIN, CRC BIN, ELF, and HEX artifacts

Provenance

The issue was identified while reviewing reliability work in bedge117/M1, specifically commit 4fa1a463dee5c224cc590eb323806a369ea1b23a (C3.157: wedge-hardening pass ...). The change here was independently reproduced against Monstatek/M1 and reduced to the one-line root-cause correction above rather than copying the larger reference patch.