feat(#23): now-playing アプリの PID を NowPlayingInfo まで伝搬

[GeneralD]

概要

スペクトラムアナライザ (#23) の前提工事として、now-playing アプリの PID を MediaRemote helper から NowPlayingInfo まで伝搬する。CoreAudio process tap（macOS 14.2+ の AudioHardwareCreateProcessTap）は対象プロセスの PID を要求するため、このパイプラインが tap 実装の入口になる。

この PR は #23 を close しない — アナライザ本体（AudioTapDataSource / SpectrumInteractor / Presenter / View / config）は後続 PR で実装する。

変更内容

media-remote-helper → MediaRemoteDataSource → NowPlaying (Entity) → TrackHandler → NowPlayingInfo

モジュール	変更
media-remote-helper.swift	MRMediaRemoteGetNowPlayingApplicationPID を 任意解決で追加。シンボル欠落時は pid なしペイロードに縮退し helper 自体は死なない。PID 0（セッション所有アプリなし）は nil に正規化
MediaRemoteDataSourceImpl	JSON ペイロードの pid フィールドをデコード
Entity/NowPlaying	pid: Int? 追加（内部エンティティ）
Entity/NowPlayingInfo	pid: Int? 追加 — lyra track の JSON 出力に pid が現れる
TrackHandlerImpl	lyrics あり／なし両パスで pid をパススルー

設計メモ

• 任意解決の理由: MRMediaRemoteGetNowPlayingApplicationPID は private symbol。将来の macOS で消えても helper 全体を殺さず、pid だけ欠落する graceful degradation にした
• PID 0 → nil: MediaRemote はセッション所有アプリ不在時に 0 を返す。クライアントに偽 PID を見せないよう helper 側で nil に正規化
• helper は引き続き /usr/bin/swift -interpret 経由（Apple-signed host 必須、bug: v2.13.3 で歌詞・トラック情報が表示されない (helper 事前コンパイル化の署名リグレッション #256) #261 の制約は不変）

テスト

• MediaRemoteDataSourceImplTests: pid ありペイロード → surfaced、pid なし → nil
• TrackHandlerImplTests: デフォルトクエリ／lyrics パス両方で passthrough を検証
• 全 978 テストパス

実機 JSON デモを載せていない理由

now-playing セッション不在の環境では lyra track が出力せず待ち続けるため、実出力を採取できなかった。変更前の brew 2.16.0 でも同一症状（コントロールテスト済み）で、この diff とは無関係の既存挙動 → #295 に起票済み。helper 単体（/usr/bin/swift <bundle>/media-remote-helper.swift）は本変更後も {"has_info":false} を即時継続出力しており、helper 側の縮退は正常。

TODO（後続）

• AudioTapDataSource（CoreAudio process tap + FFT）
• SpectrumInteractor / Presenter / View + config 層
• Add spectrum analyzer overlay #23 Open Question Use actual install path in LaunchAgent plist #3（ブラウザ PID の over-broad capture 緩和策）

Relates to #23

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds an optional pid property to NowPlaying and NowPlayingInfo entities, threads it through the media-remote-helper CLI (resolving via dlsym), fixes a missing separator in MediaRemoteDataSourceImpl.poll(), propagates pid through TrackHandlerImpl, adds tests, and bumps the version file.

Changes

PID propagation

Layer / File(s)	Summary
Entity pid property Sources/Entity/NowPlaying.swift, Sources/Entity/NowPlayingInfo.swift	Adds an optional pid: Int? property and initializer parameter (default nil) to both NowPlaying and NowPlayingInfo.
Helper PID resolution and payload Sources/MediaRemoteDataSource/Resources/media-remote-helper.swift	Resolves MRMediaRemoteGetNowPlayingApplicationPID via dlsym, splits printing into printInfo(event:pid:), and reworks fetchAndPrint to include pid in the emitted JSON.
Data source pid mapping and tests Sources/MediaRemoteDataSource/MediaRemoteDataSourceImpl.swift, Tests/MediaRemoteDataSourceTests/MediaRemoteDataSourceImplTests.swift	Fixes the NowPlaying initializer call so pid is correctly parsed after timestamp, extends the jsonLine test helper with an optional pid, and adds a test asserting pid decoding across polls.
TrackHandler pid passthrough and tests Sources/TrackHandler/TrackHandlerImpl.swift, Tests/TrackHandlerTests/TrackHandlerImplTests.swift	Reformats NowPlayingInfo initializer calls to include pid in both no-lyrics and lyrics paths, extends NowPlaying.stub with pid, and adds passthrough tests for both paths.
Version bump Sources/VersionHandler/Resources/version.txt	Updates version from 2.16.0 to 2.17.0.

Estimated code review effort: 2 (Simple) | ~12 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Timer
  participant fetchAndPrint
  participant GetPIDFn
  participant printInfo
  participant stdout

  Timer->>fetchAndPrint: event (.trackChange/.tick)
  fetchAndPrint->>GetPIDFn: resolve pid via dlsym
  GetPIDFn-->>fetchAndPrint: pid or nil (0 mapped to nil)
  fetchAndPrint->>printInfo: event, pid
  printInfo->>stdout: JSON payload with pid field

Loading

Related issues: None specified.

Related PRs: None specified.

Suggested labels: enhancement

Suggested reviewers: GeneralD

_{🐰 A hop, a skip, a pid appended,
through helper, handler, all extended,
from zero mapped to gentle nil,
the tracks now carry process still.
Version bumped, the tests all pass—
this rabbit's build is first in class! 🥕}

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: propagating the now-playing app PID to NowPlayingInfo.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/23-nowplaying-pid-pipeline

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[Copilot]

Pull request overview

This PR prepares the now-playing pipeline for the upcoming spectrum analyzer work (#23) by propagating the now-playing application PID from the MediaRemote helper output through the DataSource and Entity layers into NowPlayingInfo (surfaced by lyra track output).

Changes:

• Extend media-remote-helper.swift to (optionally) resolve MRMediaRemoteGetNowPlayingApplicationPID, normalize PID 0 to nil, and emit "pid" in the helper JSON payload.
• Decode the "pid" field in MediaRemoteDataSourceImpl, add pid: Int? to NowPlaying / NowPlayingInfo, and pass it through TrackHandlerImpl for both non-lyrics and lyrics paths.
• Add unit tests covering PID decoding and PID passthrough, and bump the app version.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Sources/MediaRemoteDataSource/Resources/media-remote-helper.swift	Optionally fetches now-playing app PID and includes it in helper JSON output (PID 0 → nil).
Sources/MediaRemoteDataSource/MediaRemoteDataSourceImpl.swift	Decodes "pid" from the helper payload into NowPlaying.
Sources/Entity/NowPlaying.swift	Adds pid: Int? to the internal now-playing entity.
Sources/TrackHandler/TrackHandlerImpl.swift	Passes pid through into NowPlayingInfo on both code paths.
Sources/Entity/NowPlayingInfo.swift	Adds pid: Int? to the public Codable output entity.
Tests/MediaRemoteDataSourceTests/MediaRemoteDataSourceImplTests.swift	Tests that PID is surfaced when present and nil when absent.
Tests/TrackHandlerTests/TrackHandlerImplTests.swift	Tests PID passthrough for default and lyrics queries.
Sources/VersionHandler/Resources/version.txt	Bumps version to 2.17.0.

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