WfmOxide 0.4.0

Three new vendors (Siglent, Teledyne LeCroy, Rohde & Schwarz) and a
faster decode path for small captures. No breaking changes.

New formats

Siglent SDS1xx4X-E (.bin). Heuristic detection (no magic bytes —
we validate channel-enable flags, record length, and sample-rate
sanity). u8 samples; offsets ported from featherfeet/siglent2csv.

Teledyne LeCroy .trc (WAVEDESC). Locates WAVEDESC in the first
64 bytes (handles SCPI block-prefixed and bare files), honours
COMM_ORDER endianness and COMM_TYPE byte/word width. Decodes the
LECROY_2_3 template common to Wave*, HDO, DDA, LC. Bit-exact against
lecroyparser on three real fixtures.

Rohde & Schwarz RTP / RTO / RTE (paired .bin + .Wfm.bin). Pass
the XML; we open its binary sibling. All four signal formats:
INT8BIT, INT16BIT, FLOAT, XYDOUBLEFLOAT (with interleaved f64
timestamps). Multi-channel interleaving handled. Bit-exact against
RigolWFM on five real RTP fixtures.

Performance

decode_with now runs serially below 256 K samples — rayon's
dispatch was dominating per-element work on small captures. The
contiguous-index path (LeCroy, Tek, ISF, Keysight) uses
chunks_exact so LLVM can autovectorise. The parallel path for
large captures is unchanged.

| File | Points | Reference | WfmOxide | Speedup |
| ----------------------------- | --------- | -------------------------- | ---------- | ------- |
| Siglent 7-Mpt @ 1 GSa/s | 7,000,000 | 8.65 ms (numpy) | 1.33 ms | 6.5× |
| LeCroy pulse.trc | 502 | 0.079 ms (lecroyparser) | 0.015 ms | 5.1× |
| LeCroy pulse_sequence.trc | 10,040 | 0.098 ms (lecroyparser) | 0.030 ms | 3.3× |
| LeCroy issue1.trc | 100,002 | 0.252 ms (lecroyparser) | 0.174 ms | 1.4× |
| R&S rs_rtp_01 (1ch f32) | 4,000 | 0.793 ms (RigolWFM) | 0.061 ms | 13.1× |
| R&S rs_rtp_03 (1ch i8) | 4,000 | 0.769 ms (RigolWFM) | 0.063 ms | 12.2× |
| R&S rs_rtp_05 (2ch XY-f32) | 4,000 | 0.756 ms (RigolWFM) | 0.076 ms | 9.9× |

Existing formats are unaffected: 0.3.0 captures decode bit-identically.

Test fixtures

Real captures only — nine new fixtures shipped:
geekman/siglent-bin2sr (Siglent), lobis/lecroy-scope (three LeCroy),
scottprahl/RigolWFM (five R&S RTP pairs).

Compatibility

No API changes; same wheel targets as 0.3.0.