[WyattBlue]

Fixes stub annotations that don't match runtime. I found them by reading every stubbed attribute and property on objects from the test assets and type-checking the real values against the annotations, which catches things stubtest can't see in Cython classes.

Runtime fixes

• HWConfig.methods raised ValueError whenever a config supported several methods (e.g. VideoToolbox h264 reports 11), because FFmpeg's methods is a bitmask but HWConfigMethod was an IntEnum. It's now an IntFlag. Added test_codec_hardware_config_methods, which fails without the fix.
• CodecContext.is_encoder, CodecContext.is_decoder, Container.input_was_opened, and VideoFormatComponent.is_chroma returned raw C ints; they now return bool.
• Frame.time_base returned None when unset; it now returns a falsy AVRational(0, 1), like every other AVRational property. Internal is None checks in AudioResampler and Graph.add_buffer/add_abuffer now test truthiness. Code checking frame.time_base is None should use not frame.time_base.

Stub fixes

• average_rate, base_rate, and guessed_rate moved from Stream to VideoStream, the only class that defines them.
• codec, codec_tag, and options moved from Stream to AudioStream, VideoStream, and SubtitleStream, which forward them to their codec context. DataStream and AttachmentStream don't forward and raise AttributeError. options is now dict[str, str] there, matching CodecContext.options: non-str values made open() raise TypeError.
• Stream.codec_context is CodecContext | None; DataStream and AttachmentStream declare it as None.
• Now optional: AudioStream.bit_rate, InputContainer.start_time, VideoFrame.time, and FilterPad.context (FilterContextPad.context stays non-optional).
• Codec.hardware_configs is tuple[HWConfig, ...], not list; CodecContext.delay is int, not bool.
• Added AudioStream.max_bit_rate.
• Removed Plane.frame, Plane.index, and Container.buffer_size, which are private cdef fields.

Notes

• Possible break for type-checked code: container.streams[0].codec (a plain Stream) no longer type-checks, matching runtime for data streams. Narrow first, e.g. container.streams.video[0] or an isinstance check.
• Several tests were partly unreachable to mypy, because asserts like bit_rate is None contradicted the old stubs. They're now checked, and needed three small edits: two isinstance(..., av.VideoStream) asserts and streams.subtitles[0] in place of streams[0].
• Not fixed: streams from add_mux_stream() have codec_context is None, and AudioStream.format/VideoStream.format can be None, but the stubs say otherwise. Making these optional would force None checks into most stream-handling code, so they're left for a separate decision.