Beagle SCM

CODE-010: spot: unify grep/pcre cbs + trigram scan

spot/GREP.c's capo_grep_file_cb and capo_pcre_file_cb share a byte-identical tokenize-and-mark prologue and overall skeleton, and the trigram off-block scan is pasted between CAPO.c and GREP.c (with a manual u64css→seek_runs[] copy on both sides). Factor the shared callback core and the off-block scan; use an abc slice-array copy.

Issues

The two grep callbacks and the trigram off-block scan are each duplicated.

• capo_grep_file_cb/capo_pcre_file_cb (GREP.c:58-156/300-400) share the tokenize prologue + hls state skeleton.
• trigram off-block scan pasted CAPO.c:1244 (literal) vs GREP.c:217 (regex).
• u64css live→seek_runsCAPO_MAX_LEVELS hand-copy twice (CAPO.c:1253, GREP.c:224); plus 4-ptr arena copies.

Blockers

None; spot-internal.

Planned

One shared callback core + one off-block scan helper; an abc slice-array copy.

• Repro first (§17): spot grep + pcre search results over the fixture stay identical.
• Extract the tokenize/mark prologue + hunk-emit skeleton; both cbs call it.
• One trigram off-block scan; replace the manual seek_runs copy with an abc slice copy.