Upgrade vendored FFF to 0.10.5

[vmg-dev]

Summary

• rebase the documented FFF Swift integration delta onto upstream FFF 0.10.5
• retain the C static library bridge, binary-file filtering, and watcher directory handling
• record upstream tag provenance in UPSTREAM.md

Verification

• cargo test --workspace
• cargo clippy --package fff-search --package fff-c --lib -- -D warnings
• swift test (FFFKit: 2 tests)
• Floodlight swift test against the local package (52 tests passed; 1 opt-in benchmark skipped)

The upstream all-target Clippy run currently reports warnings in upstream test fixtures on the installed Rust toolchain; production libraries pass with warnings denied.