Add samsond codec: 7,564,554 bytes

[samsond]

Implements sequential delta encoding with first-occurrence dictionary ordering to exploit temporal locality in the event stream.

Approach:

• Repos indexed by first appearance order for minimal delta jumps
• Continuous delta encoding across entire stream (no block resets)
• Lossless (name, id) tuple keys handle duplicate repo names
• Prefix-compressed dictionaries with zstd(22) final pass

Optimized for unsorted (temporal order) input to preserve locality.

[agavra]

Congrats @samsond this is great! I confirmed your score in CI/CD:

┌────────────────────────┬────────────────┬────────────┐
│ Codec                  │           Size │ vs Naive   │
├────────────────────────┼────────────────┼────────────┤
│ Naive                  │    210,727,389 │   baseline │
│ samsond                │      7,564,554 │     -96.4% │
└────────────────────────┴────────────────┴────────────┘

CI/CD failed because of format but I can just fix that when I add you to the leaderboard.