fix(ios): return frame-count duration from IOSFileWriter::closeFile

[wildseansy]

Closes # — no existing issue tracks this.

⚠️ Breaking changes ⚠️

Introduced changes

• IOSFileWriter::closeFile() returned AVURLAsset.duration for the file it had just closed. For containerless streams such as raw AAC in ADTS framing (feat: add ADTS AAC file format for crash-recoverable compressed recording #1319) AVFoundation has no stored duration and estimates size ÷ bitrate of the first packets. With VBR AAC and a quiet opening that estimate runs 20–70 % long: 30 s recordings were reported as 38, 44, 41 and 39 s.
• closeFile() now returns getCurrentDuration() (frames written ÷ file sample rate), read after offloader_.reset() has drained every queued buffer so the count is final. This matches what the recorder already reports mid-recording and what the Android writer returns at stop, and removes an AVFoundation asset open from the stop path.
• Other paths checked: pause/resume writes nothing while paused, so file and count agree; an input-format change keeps framesWritten_ and counts at the file sample rate on the converter path; dropped buffers are skipped in both the file and the count; IOSRotatingFileWriter sums per-segment closeFile() durations and each segment has its own counter.

Checklist

• Linked relevant issue — none exists
• Updated relevant documentation — N/A, FileInfo.duration semantics are unchanged
• Added/Conducted relevant tests — manual, see below; iOS Objective-C++ has no unit harness in the repo (gtests cover common C++)
• Performed self-review of the code
• Updated Web Audio API coverage — N/A
• Added support for web — N/A, iOS-only writer
• Updated old arch android spec file — N/A

Verification

• Synthetic quiet-then-loud ADTS file, real length 25.0 s: the AVURLAsset estimate reports 37.6 s, the frame count reports 25.0 s.
• iOS simulator, ADTS recordings auto-stopped at 30 s of audio (1300–1334 AAC frames ≈ 30.2–31.0 s): before this change stop() reported 38, 44, 41, 39 and 31 s.
• iOS simulator with this change: record → pause → resume → stop reports a duration that excludes the paused time and matches ffprobe -count_packets × 1024 ÷ 44100 within 1 s.
• Note: a decoded raw ADTS file plays ~50 ms longer than the frame count because of AAC priming and last-packet padding; the frame count is the content length.
• clang-format 23 and commitlint (config-conventional) clean.

🤖 Generated with Claude Code

[github-actions]

WPT non-regression comparison

PASS — no regressions · 0 improved section(s) · overall 2717 → 2717 (0)

Unchanged sections (28)

Spec section	Base pass	Head pass	Delta
Processing model	0	0	0
Other	52	52	0
AnalyserNode	138	138	0
AudioBuffer	140	140	0
AudioBufferSourceNode	218	218	0
AudioContext	58	58	0
AudioNode	261	261	0
AudioParam	629	629	0
BiquadFilterNode	275	275	0
ChannelMergerNode	30	30	0
ChannelSplitterNode	7	7	0
ConstantSourceNode	64	64	0
ConvolverNode	203	203	0
DelayNode	104	104	0
DestinationNode	0	0	0
DynamicsCompressorNode	4	4	0
GainNode	15	15	0
IIRFilterNode	87	87	0
MediaElementAudioSourceNode	0	0	0
MediaStreamAudioDestinationNode	1	1	0
MediaStreamAudioSourceNode	0	0	0
OfflineAudioContext	35	35	0
OscillatorNode	104	104	0
PannerNode	75	75	0
PeriodicWave	33	33	0
ScriptProcessorNode	0	0	0
StereoPannerNode	102	102	0
WaveShaperNode	82	82	0

_{Baseline: 0494fdc08c00b4cea1927d3b66df8b2c6416760a · Candidate: 03b9ec8b751cd387c47521625d60d620ec5d32ff}

_{Workflow run · this comment is updated on every push.}