docs: correct the _perf path references after the bench moved

The `_perf/` measurement bench was gitignored and had never been committed, so
23 of the 27 scripts cited by the perf documents were already lost. The 11
surviving files (4 scripts, cfg_dm1.json, 5 result JSONs, the 53 MB MJPG clip)
have been moved to D:\orisys_ws\docs\performance\perf-measurements\ and the
scripts patched to resolve their defaults next to themselves. The directory has
been removed from this repo.

These three files said the scripts were deleted, which was only half true:
they are moved, and the four surviving ones still run. Repointed:

- src/orisys/sensor.py: the FILTER_PRESETS comment now names the real location
  (comment only; FILTER_PRESETS itself is unchanged).
- docs/filters.md and examples/filters/README.md: the same correction for the
  latency/noise measurement provenance.

No behaviour change.

examples/filters/README.md

@@ -7,8 +7,8 @@
 配置里**没写**的滤波键等于"关"：整段删掉就是什么都不滤，和 `off` 那段等价。
 
 背景、代价与可追溯性约定见 `docs/filters.md`；延迟/噪声实测见
-`D:\orisys_ws\docs\performance\orisys-sdk-perf-plan.md`（原 `_perf/` 测量脚本已删除，
-该文档保留全部实测数字）。
+`D:\orisys_ws\docs\performance\orisys-sdk-perf-plan.md`（原 `_perf/` 已从本仓库移除：幸存脚本与
+片源在 `D:\orisys_ws\docs\performance\perf-measurements\`，该文档保留全部实测数字）。
 
 下面每一段都有一个同目录的机器可读副本 `filters_<预设名>.json`（四个文件），
 `tests/test_filter_presets.py` 会核对它们与 `FILTER_PRESETS` 完全一致 —— 所以改预设时