feat(cmcd): upgrade to CMCD v2 using @svta/cml-cmcd CmcdReporter

[littlespex]

Summary

Implements CMCD v2 support by migrating from @svta/common-media-library to the dedicated @svta/cml-* packages and fully delegating CMCD encoding to CmcdReporter from @svta/cml-cmcd.

Resolves #7723.

Changes

• Migrate dependencies: Replace @svta/common-media-library with @svta/cml-cmcd, @svta/cml-id3, @svta/cml-utils, and @svta/cml-structured-field-values
• CMCD v2 data fields: Add version, st (stream type), sta (player state), sn (sequence number) to CMCD output. Inner list encoding for br, tb, bl, mtp, nor per v2 spec
• CmcdReporter integration: Delegate all CMCD request encoding to CmcdReporter.createRequestReport(), removing manual appendCmcdHeaders/appendCmcdQuery calls and the createData() method
• Event-mode reporting: Support v2 event targets for play state changes (PLAY_STATE), fatal errors (ERROR), and bitrate changes (BITRATE_CHANGE)
• Configuration: Add version, enabledKeys, and eventTargets to CMCDControllerConfig. Default enabledKeys to CMCD_V1_KEYS (v1) or CMCD_KEYS (v2)
• Exported types: Re-export CMCD v2 types (CmcdVersion, CmcdPlayerState, CmcdStreamType, etc.) from exports-named.ts
• Tests: Comprehensive unit test coverage for v1 defaults, v2 fields (query and headers modes), stream type detection, event reporting, and reporter lifecycle

Behavioral notes

• v=1 is omitted from output per CMCD spec (it is the default)
• sn (sequence number) is automatically included in v2 output, filtered out for v1
• nor uses root-relative paths (via url.origin as baseUrl) instead of path-relative
• Inner list values (bl, tb) are guarded against NaN to prevent Structured Fields serialization errors

Test plan

• All 912 unit tests pass
• Manual verification with a CMCD v1 configuration (query and headers modes)
• Manual verification with a CMCD v2 configuration (query, headers, and event modes)
• Verify no source map warnings in downstream bundlers (Vite/Nuxt)

[littlespex]

@robwalch I'm not sure about this check. Is there a better way to determine if a stream is low latency?

[robwalch]

Good question!

Only checking EXT-X-SERVER-CONTROL for blocking reload or delta playlist capabilities is not enough. Both of these features can be used without partial segments (details.partList) for live playback at a standard three target duration hold back.

If we follow the requirements of a "Low-Latency Server Configuration Profile":

if (
  // Playlist has EXT-X-PROGRAM-DATE-TIME
  details.hasProgramDateTime &&
    
  // Segments have at least one key-frame (EXT-X-INDEPENDENT-SEGMENTS or track violations)
  // skip this requirement - something like `couldBacktrack` on LevelDetails could be nice to have
    
  // Playlist has EXT-X-PART(s)
  !!details.partList &&

  // Playlist has EXT-X-PRELOAD-HINT
  // skip this requirement - support will be added with #6356
    
  // Playlists has at least one EXT-X-RENDITION-REPORT or only one variant
  (!!details.renditionReports || this.hls.levels.length === 1) &&
    
    // Blocking Playlist Reload is required
    details.canBlockReload
) {
  return CmcdStreamType.LOW_LATENCY;
}

Delta playlists are not required because playlist can be short enough that skipping segments doesn't add much if any benefit. Blocking reload is critical - servers that don't implement it, and worse only signal they do, perform miserably. HLS.js today may still use parts without PDT and Rendition Reports (I'll have to check), but it should not. I'll file an issue to follow up with other scheduled LL-HLS enhancements.

[robwalch]

• Filed Make sure Low-Latency Server Configuration Profile is met before using Parts #7729

[littlespex]

I'm not sure if these should just be merged with the tests/unit/controller/cmcd-controller.ts tests. They are different in that they actually load media and inspect the outgoing traffic for correct CMCD data.

[littlespex]

This helper monkey patches fetch so that outgoing requests can be inspected. It also acts as an "event" server for CMCD event mode, generating the 204 response.