Add T13-T18 Phase 9 verification tests; ASCII cleanup across codebase

Tests added (tests/unit/run_tests.py):

• T13: pure-Python PackPeptide/UnpackPeptide round-trip for all 20 AAs x len 8-12; I/L canonicalization; integer sort == lex sort; known value for ACDEFGHI. 120 checks PASS.
• T14: boundary FASTA (14-AA, len 12-13 no-enzyme); exactly 5 peptides split across short/long paths, each mapping to 1 protein. PASS.
• T15a/b: I/L canonicalization for short (len 8) and long (len 13) paths; equal_IL=1 merges I/L pairs to 1 entry with 2 proteins; equal_IL=0 keeps both separate. PASS.
• T16: two identical 13-AA proteins; 21 unique peptides (len 8-13), every entry maps to 2 proteins (validates cross-path protein list correctness). PASS.
• T17 (–integration): builds human.small.fasta (no-enzyme, len 8-13, equal_IL=1); verifies peptide count in [8.8M, 9.1M] and count == protein-list count. PASS.
• T18 (–integration): two stratified builds of human.small.fasta are byte-identical. PASS.

New FASTA fixtures: t14_boundary, t15_IL_short, t15_IL_long, t16_crosspath.

Also replaces all non-ASCII characters in source and documentation files with ASCII equivalents (em-dash, arrows, checkboxes, special symbols, Cyrillic A, BOM), per CLAUDE.md coding style directive. Third-party file BS_thread_pool.hpp excluded.