[oemasync]

locate_extab_extabindex() probes for _eti_init_info at
section_end - ETI_INIT_INFO_SIZE * (num_text_sections + 1) and walks forward, reading a candidate table at each
address. A section's size can stop short of the next section: sizes come from _rom_copy_info, whose values are
rounded differently from the file's. The first candidate then lands in the gap, read_eti_init_info() fails
(Failed to locate section @ <addr>), and the ? on it abandons the search for the whole program — so
extab/extabindex are never named.

Consequences:

• The game splits with no exception-table splits at all (silent, wrong output).
• Once anything names an extabindex section, the split fails hard instead:
  Failed to find extab section.

Reproduction

dtk dol split on v1.8.4:

• Sonic Adventure 2 Battle (GSNE8P) DOL: WARN Failed to locate extab/etabindex: Failed to locate section @ 0x80173124 (this program has no extab, so the warning was all you saw).
• Animal Crossing (GAFE01) section layout: .init at 0x80003100 with a copied size of 0x2500 (file size
  0x2520), extab at 0x80005620, extabindex at 0x80005660, _eti_init_info at 0x80005684. Number of code
  sections is 2, so the first probe for the extab section is 0x80005648 - 48 = 0x80005618, which is in the gap
  between .init's copied end (0x800055F0/0x80005600) and 0x80005620 → Failed to locate section @ 0x80005618,
  and the exception tables are never named.

Change

• Clamp the first candidate to the section start (saturating_sub(..).max(section_start)), so a small section can't
  underflow the probe below its own start.
• Treat an unreadable candidate as "not this one" (continue) instead of returning an error for the whole program.
• Give the end-of-table read in the second loop a message that says what it was doing.

Verification

• Sonic Adventure 2 Battle DOL: no warning, and build/config.json, config/*/splits.txt, config/*/symbols.txt
  are byte-identical to v1.8.4 (the patch is inert for programs without exception tables).
• Animal Crossing-layout DOL: the Failed to locate section @ 0x80005618 warning is gone and extab/extabindex
  are named, with @eti_* symbols created the way they are for every other game.