fix(jitdump): support MacOS u64 tid fields#1
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Add end-to-end parse tests over real cpython perf jitdump captures: a Linux x86_64 dump in the standard layout (u32 tid) and a macOS arm64 dump in the wider layout (u64 tid + alignment padding). Each must yield 195 CODE_LOAD + 195 CODE_UNWINDING_INFO records, exercising the per-record layout detection.
CPython on macOS declares the jitdump thread_id as uint64_t (filled via pthread_threadid_np) instead of the perf spec's uint32_t, adding 8 bytes (wider field + alignment padding) that shift the name and code bytes in every CODE_LOAD/CODE_MOVE record. The u32-only parser misread code_size as the code address and failed to parse these files at all. Widen tid to u64 and detect the layout per record from the body length: try the standard layout first, fall back to the wider macOS layout when the field offsets are not self-consistent with the record size.
try_parse now returns Result<Option<Self>, io::Error>: Ok(None) signals only a layout mismatch, while genuine read errors (e.g. UnexpectedEof on a truncated record) propagate. The narrower standard layout's read errors surface as truncation; the wider layout's are treated as "not this layout". Adds a regression test. Addresses PR #3 review feedback.
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