chore: add ASAM OpenX standards submodule

Add ASCS-eV/asam-openx-standards as a submodule at submodule/asam-openx-standards/
to provide authoritative ASAM OSI and OpenDRIVE spec references directly
in the repository. This replaces inline URLs with traceable,
version-pinned standard definitions.

Also updates agent instructions (AGENTS.md, .github/copilot-instructions.md)
to document the submodule location.

Signed-off-by: Carlo van Driesten <carlo.van-driesten@bmw.de>

Author: jdsika

.github/copilot-instructions.md

@@ -70,6 +70,11 @@ This is a **Lichtblick extension** that registers message converters to transfor
 - `entityPrefixes.ts`: String prefixes for entity IDs (e.g., `PREFIX_LANE`, `PREFIX_TRAFFIC_LIGHT`)
 - `frameTransformNames.ts`: Coordinate frame naming constants
 
+**Standards** (`submodule/asam-openx-standards/`)
+- `standards/asam-osi/` — Authoritative ASAM OSI proto definitions and spec
+- `standards/asam-opendrive/` — ASAM OpenDRIVE spec (for cross-referencing geo-referencing)
+- Use these for verifying standard compliance rather than external URLs
+
 ### Message Converter Pattern
 
 Converters follow this structure:

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "submodule/asam-openx-standards"]
+	path = submodule/asam-openx-standards
+	url = https://github.com/ASCS-eV/asam-openx-standards.git

AGENTS.md

@@ -14,6 +14,10 @@
 - `example-data/`: Sample OSI/MCAP inputs for local testing.
 - `dist/`: Build output generated by `yarn run build` or `yarn run package`.
 - `docs/`: Project documentation and plans.
+- `submodule/asam-openx-standards/`: **ASAM OpenX standards submodule** — authoritative spec references:
+  - `submodule/asam-openx-standards/standards/asam-osi/` — ASAM OSI spec (proto definitions)
+  - `submodule/asam-openx-standards/standards/asam-opendrive/` — ASAM OpenDRIVE spec
+  - Use these for verifying standard compliance rather than external URLs
 
 ## Build, Test, and Development Commands