fix(parallel): destroy thread parser before slab reclaim in LSP-cross loop

The LSP-cross loop in parallel_resolve called cbm_slab_reclaim() without
first destroying the thread-local tree-sitter parser, violating the
documented slab contract. The parser's lexer holds slab-allocated state
(notably lexer.included_ranges, a 24-byte allocation that lands in the
≤64B slab bucket); reclaiming the slab leaves that pointer dangling.

Workers don't trip on it because they don't reparse afterward, but the
main thread participates in cbm_parallel_for and any later cbm_extract_file
on the main thread — including the sequential pass_definitions in the
incremental pipeline — hits a heap-use-after-free in ts_lexer_goto on
macOS-ASan.

Two-part fix:
- pass_parallel.c: destroy the thread parser before cbm_slab_reclaim() in
  the per-file LSP-cross loop, matching the worker extract loop.
- pass_definitions.c: defensively drop the thread parser at pass entry so
  the incremental sequential path cannot inherit stale state from any
  prior run.