Handle sammyfirm streaming mode - use extracted .lz4 files directly

[Copilot]

sammyfirm now downloads firmware in streaming mode, extracting directly to .lz4 files without creating intermediate AP_*.tar.md5 archives. Build scripts expected the tar archives and failed with "AP file not found".

Changes

scripts/download_utils.sh

• Detect streaming mode by checking for super.img.lz4 when AP_*.tar.md5 is absent
• Skip tar validation for streaming mode, validate essential .lz4 files exist instead
• Maintain backward compatibility with traditional tar.md5 mode

scripts/unpack_fw.sh

• Detect streaming mode and decompress super.img.lz4 directly via lz4 -d
• Use .lz4 file stats for cache validation in streaming mode
• Fall back to traditional tar extraction when AP_*.tar.md5 exists

Both modes coexist: traditional (tar.md5 → extract → decompress) and streaming (direct .lz4 → decompress).

# Streaming mode detection
if [[ -z "$ap_file" ]]; then
    if [[ -f "$odin_dir/super.img.lz4" ]]; then
        streaming_mode=true
        # Direct decompression: lz4 -d super.img.lz4 super.img
    fi
fi

Original prompt

Fix https://productionresultssa3.blob.core.windows.net/actions-results/699e21b5-f277-47a6-966b-8ef0107753bd/workflow-job-run-7e10ee9a-bc6b-5052-9e3f-9b396273f4f6/logs/job/job-logs.txt?rsct=text%2Fplain&se=2025-12-30T20%3A54%3A43Z&sig=3PJCFojsoxVtdowWZsrGAVWcRr57L7w8EQYpO9CaKtM%3D&ske=2025-12-31T05%3A54%3A03Z&skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb&sks=b&skt=2025-12-30T17%3A54%3A03Z&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skv=2025-11-05&sp=r&spr=https&sr=b&st=2025-12-30T20%3A44%3A38Z&sv=2025-11-05

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