fix: macOS arm64 compat for way-match and test scripts

[0x3dge]

Summary

• Rebuild bin/way-match as native arm64 Mach-O (was Linux x86-64 ELF, failing with exec format error)
• Fix test-harness.sh and test-integration.sh for bash 3.2 (macOS default) — replace declare -A and mapfile with indexed arrays and while-read loops
• Add /sync-upstream skill to automate pulling changes from aaronsb/claude-code-config while preserving our platform fixes

Test plan

• way-match --version runs on arm64 macOS
• way-match pair correctly matches and rejects (3 end-to-end tests via match-way.sh)
• way-match suggest analyzes a real way.md file
• Test harness runs on bash 3.2: 72/74 accuracy (97.3%), 0 false positives
• /sync-upstream skill detected by skill system

[0x3dge]

Hey! I forked this to run on macOS (arm64 Apple Silicon) and hit a couple of issues. Here's what this PR fixes and why:

1. bin/way-match binary — Linux ELF on macOS

The checked-in binary is a Linux x86-64 ELF:

$ file bin/way-match
bin/way-match: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV)...

macOS can't execute this — it needs a Mach-O binary (or a Cosmopolitan APE, which the Makefile supports but isn't what was checked in). The fix here is just make local which rebuilds with the system compiler. The Makefile already has the local target, so the tooling was there — just the checked-in binary wasn't cross-platform.

Suggestion for upstream: Either ship a Cosmopolitan APE binary (which runs on both Linux and macOS), or don't check in the binary at all and have users run make local. The cosmocc build target in the Makefile would produce a universal binary if you have the Cosmopolitan toolchain installed.

2. Test scripts use bash 4+ features

macOS ships bash 3.2 (Apple won't ship bash 4+ due to GPLv3 licensing). Both test-harness.sh and test-integration.sh use:

• declare -A (associative arrays) — bash 4+ only
• mapfile -t — bash 4+ only

These fail immediately on macOS:

declare: -A: invalid option

The fix replaces these with bash 3.2 compatible patterns:

• Parallel indexed arrays + a lookup function instead of associative arrays
• while IFS= read -r loop instead of mapfile

No behavior change — same test cases, same output format, same results. Just works on both platforms now.

Results after fixes

Everything works on macOS arm64:

• Binary runs, all three modes (pair, score, suggest) functional
• Test harness: 72/74 accuracy (97.3%), 0 false positives, all 10 co-activation tests pass
• Hook integration (match-way.sh) correctly detects and uses the BM25 engine

Happy to help if you have questions about the macOS side of things!