refactor(types): split media_common.rs by media domain

[devin-ai-integration]

Summary

types/entities/media_common.rs was a flat 458-line file bundling
audio, video, transport, desktop, and error payload types in one
place. Split into a directory-first module per the AGENTS.md
guideline ("split when a module grows beyond ~400-600 lines or
mixes multiple responsibilities"):

• media_common/mod.rs - module wiring + re-exports.
• media_common/audio.rs - JitterConfig, AudioFormat,
  AudioInputProgress.
• media_common/video.rs - VideoFormat, VideoCodec,
  VideoFrame.
• media_common/transport.rs - EncryptionContext,
  ClientKeepAlive, AbusePrevention.
• media_common/desktop.rs - DesktopInput.
• media_common/error.rs - ErrorMessage.

The parent types/entities/mod.rs kept its

mod media_common;
pub use media_common::*;

so every downstream user of the flat glob export (types::JitterConfig,
types::VideoFormat, types::EncryptionContext, etc.) continues to
resolve unchanged.

Structural only, no semantic change:

• Struct field visibility, #[non_exhaustive] derives, and method
  bodies are byte-for-byte identical to the pre-split file.
• Added minimal doc comments on public fields where
  missing_docs = "deny" started flagging them in their new homes
  (no behavioral effect).
• Kept the unsafe { ... } bindgen-union accessors in
  video.rs::VideoCodec::{from, to_ffi} bit-for-bit identical.
• Kept EncryptionContext::to_ffi raw pointer
  copy_nonoverlapping logic bit-for-bit identical (no change to
  the 511-byte clamps or the utils::ToTT call sites).

Local verification:

• cargo fmt --all --check clean
• cargo clippy --workspace --all-targets --all-features -- -D warnings clean
• cargo test --workspace --all-features -> 287 passed / 0 failed

Review & Testing Checklist for Human

• Spot-check re-exports: types::{JitterConfig, AudioFormat, AudioInputProgress, VideoFormat, VideoCodec, VideoFrame, EncryptionContext, ClientKeepAlive, AbusePrevention, DesktopInput, ErrorMessage} all continue to resolve. The
  parent glob pub use media_common::*; is unchanged.
• Confirm the domain groupings are reasonable: audio =
  jitter + audio format + input progress; video = video
  format + codec + frame metadata; transport = TLS + keep-
  alive + rate limiting; desktop = input packet; error =
  SDK error payload. JitterConfig lives under audio/
  because it is primarily an audio jitter buffer knob.
• Verify the unsafe blocks in video.rs::VideoCodec still
  match the original FFI union layout exactly (they do -
  byte-for-byte copy from the pre-split file) and that the
  511-byte clamp logic in transport.rs::EncryptionContext::to_ffi
  is unchanged.

Notes

Next PR in the P0 structural refactor queue after #44-#49.
Independent of the other refactor PRs so can be merged in any
order.

Upcoming: split client/backend.rs (1334 lines) +
client/backend_mock.rs (1101 lines) pair; then P1 API tweaks
(full-jitter ExponentialBackoff, StreamTypes, SdkErrorCode,
TimeoutKind, SecretString, indexed dispatch) each with their
own tests; then a big test-fill PR driven by
scripts/audit_teamtalk_coverage.py.

The pre-existing semver CI gate is expected to remain red;
release-plz handles the eventual version bump.

Link to Devin session: https://app.devin.ai/sessions/71fdd6196cb74723a2e277bb81993a9c
Requested by: @BlindMaster24

---

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.