e2ee: add AV1 support

[am-sokolov]

Summary

Adds AV1 support to insertable-stream E2EE by selectively encrypting AV1 OBU payload bytes while keeping routing/keyframe-relevant bits in the clear, and by appending E2EE metadata as a standards-compliant OBU_METADATA.

Motivation

• The SDK already supports publishing AV1, but E2EE previously rejected AV1 frames (av1 is not yet supported for end to end encryption), making AV1 unusable when E2EE is enabled.

What’s in this PR

• src/e2ee/E2eeManager.ts
  • Forward the configured video codec (room.options.publishDefaults.videoCodec) to the E2EE worker when wiring sender transforms so the worker can run codec-specific crypto.
• src/e2ee/worker/FrameCryptor.ts
  • Implement AV1 encrypt/decrypt paths.
  • On encrypt: compute an AV1 “encryption layout”, AES-GCM encrypt only the protected ranges, insert ciphertext back into the frame, and append a final AV1 metadata OBU (key index + IV + auth tag).
  • On decrypt: extract metadata OBU, decrypt protected ranges, restore the original payload, and forward to decoder.
  • Drop frames + emit CryptorEvent.Error when AV1 layout detection fails or metadata is missing (prevents passing undecodable/corrupt frames downstream).
• src/e2ee/worker/av1Utils.ts
  • New AV1 helpers:
    • Parse OBU headers and leb128 size fields.
    • Compute protected vs. clear byte ranges (preserving keyframe-detection bits).
    • Serialize/deserialize the E2EE metadata OBU (LK magic, versioned payload).
• src/e2ee/worker/FrameCryptor.test.ts
  • Unit tests for AV1 round-trip encryption/decryption (Chromium OBU stream w/ size fields) and failure behavior when layout detection is impossible.

Design notes

What remains in clear (to preserve SFU routing + keyframe detection)

• OBU headers + extension/size fields
• External length fields (when present)
• First payload byte of OBU_FRAME_HEADER / OBU_FRAME (contains show_existing_frame / frame_type)

Metadata OBU format (appended as the last OBU)

• OBU_METADATA (type 5), payload length = 32 bytes:
  • bytes 0..1: 0x4c 0x4b ("LK")
  • byte 2: version = 1
  • byte 3: key index
  • bytes 4..15: IV (12 bytes)
  • bytes 16..31: AES-GCM auth tag (16 bytes)

Crypto

• Reuses the existing key management + IV derivation approach and AES-GCM.
• AV1 path currently uses empty AAD (clear bytes are preserved but not authenticated).

Testing

• pnpm test (Vitest)

Notes / limitations

• Receiver expects the AV1 metadata OBU to be present and last; frames without it are dropped.
• Layout detection is best-effort; if the payload doesn’t match supported AV1 layouts, the frame is dropped and an error is emitted.
• Per-frame overhead: metadata OBU (header + leb128 length + 32 bytes).

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Latest commit: 4bf38ed

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