fix(always-on): apply snapshot ignores before size checks

[snvtac]

Summary

• Apply snapshot ignore rules to every path segment during size estimation and filtered copies.
• Recursively prune ignored files and directories after clonefile/reflink snapshots.
• Fall back to filtered fs.cp if clonefile/reflink pruning cannot complete.
• Add a regression test for nested node_modules, dist, and .git paths that should not count toward maxBytes or remain in the snapshot.

Fixes #262

Testing

• npm test
• npm exec tsc -- -p tsconfig.json --noEmit
• node --import tsx --test --test-force-exit --test-timeout 60000 tests/always-on/workspace/SnapshotCopyProvider.test.ts