Add generalized capacitor GDS layout registry

Add 3,683 matched GeneralizedCapNInterdigital GDS artifacts, a Parquet manifest, layer semantics, checksums, and source links to SQuADDS_DB. Seven local layouts without matching simulation data are intentionally excluded.

README.md

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+---
+license: mit
+configs:
+- config_name: layout-manifest
+  data_files:
+  - split: train
+    path: "metadata/manifest.parquet"
+tags:
+- quantum
+- superconducting
+- qiskit-metal
+- gds
+- layout
+- quantum-hardware
+pretty_name: SQuADDS Layouts
+---
+
+# SQuADDS Layouts
+
+Versioned GDS layout artifacts for the [SQuADDS simulation database](https://huggingface.co/datasets/SQuADDS/SQuADDS_DB).
+
+This initial release contains 3,683 `GeneralizedCapNInterdigital` layouts that
+match the `coupler-GeneralizedCapNInterdigital-cap_matrix` simulation rows.
+Each layout is recorded in `metadata/manifest.parquet` with a stable layout ID,
+an exact-file SHA-256 checksum, its originating simulation `source_id`, and
+geometry metadata extracted in micrometers.
+
+## Access
+
+Use the `layout-manifest` configuration to query metadata, then download one
+raw GDS file by its `gds_path`. The SQuADDS Python `LayoutClient` verifies the
+checksum before returning the local cache path.
+
+The raw files are organized under:
+
+```text
+raw/GeneralizedCapNInterdigital/<campaign>/<instance>.gds
+```
+
+## Layer Semantics
+
+The current generalized capacitor layout convention is documented in
+`metadata/layer-semantics-v1.json`. The GDS files retain their original
+simulation-domain geometry, ports, and layer/datatype pairs.
+
+## Provenance
+
+The paired generalized capacitor simulation data was contributed by Saikat Das
+of the Levenson-Falk Lab at USC. This repository excludes seven local GDS files
+that did not have matching simulation rows.

metadata/layer-semantics-v1.json

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+{
+  "schema_version": "1.0.0",
+  "component_name": "GeneralizedCapNInterdigital",
+  "units": "um",
+  "layers": [
+    {"layer": 1, "datatype": 10, "semantic": "signal_conductors"},
+    {"layer": 1, "datatype": 0, "semantic": "ground_simulation_domain"},
+    {"layer": 2, "datatype": 0, "semantic": "north_port"},
+    {"layer": 3, "datatype": 0, "semantic": "south_port"}
+  ]
+}

metadata/manifest.parquet

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+version https://git-lfs.github.com/spec/v1
+oid sha256:159d1e4e923191f1aced00fa3de7feb810a4ff130d07542c7734614372916d46
+size 872073