Extract graph resource ordering

[sabino]

Summary

• move canonical graph resource ordering from src/project.zig into src/project/resolve.zig
• replace six facade sort calls with sortGraphResources
• add native Zig coverage for deterministic unique_id ordering across nodes, tests, sources, exposures, docs, and macros
• update PLAN.md ownership notes for resolve.zig

Validation

• zig fmt --check src/project.zig src/project/resolve.zig
• git diff --check
• changed-file private/secret/path scan: no matches
• timeout 180s zig test src/project/resolve.zig --cache-dir /tmp/dxt-zig-cache --global-cache-dir /tmp/dxt-zig-global-cache (20 passed)
• timeout 180s zig build --cache-dir /tmp/dxt-zig-cache --global-cache-dir /tmp/dxt-zig-global-cache
• timeout 240s zig build test --cache-dir /tmp/dxt-zig-cache --global-cache-dir /tmp/dxt-zig-global-cache
• timeout 240s zig build -Doptimize=ReleaseSafe --cache-dir /tmp/dxt-zig-cache --global-cache-dir /tmp/dxt-zig-global-cache
• python scripts/check_runtime_boundary.py && python scripts/check_public_safety.py
• pytest -q tests/test_cli.py (48 passed)
• pytest -q (52 passed)

Agent review

• subagent explorer recommended this graph-ordering slice as PR-sized
• codex exec preplan recommended deferring a different resolver-helper move
• codex exec diff review: No blocking findings.