Add agent onboarding documentation and cross platform validation

AGENTS.md

@@ -0,0 +1,35 @@
+# Clear Lake Watch - Agent Instructions
+
+Welcome, coding agents and contributors! Clear Lake Watch is a public environmental monitoring dashboard for Clear Lake, CA. It integrates public environmental data and uses cautious boundary language.
+
+**Purpose:**
+It organizes Clear Lake environmental context, source freshness, map review status, and cautious methodology notes.
+It must not present itself as official public-health guidance, emergency guidance, a validated forecast, or a deployed sensor network.
+
+**Safe to Edit:**
+- UI components, HTML structure, and CSS styling (without changing the meaning of the data or boundary language).
+- Documentation (clarifications, typo fixes).
+- Validation scripts and helpers (e.g., `scripts/validate-public-mirror.py`).
+
+**Do NOT Change Casually:**
+- Environmental data values (e.g., files under `data/`).
+- FHABS, USGS, OpenStreetMap, or source-status claims.
+- Site arm assignments or local-review statuses.
+- Map logic or dashboard behavior related to data interpretation.
+
+**Public-Safety Boundary Language:**
+You must preserve the following boundaries and wording:
+- The dashboard is a "late prototype / early MVP".
+- It is "not official public-health guidance", "not an official advisory", "not emergency guidance", "not a validated forecast", and "not a deployed sensor network".
+- Weather context is a "reviewed public-source snapshot" and remains "separate from lake-health interpretation".
+
+**Validation Commands:**
+Before proposing any changes, you must run the validation checks:
+- Existing PowerShell validation (if supported): `powershell -NoProfile -ExecutionPolicy Bypass -File .\scripts\validate-public-mirror.ps1`
+- Python cross-platform validation: `python scripts/validate-public-mirror.py`
+
+**Strict Warnings:**
+- Do NOT invent data, advisory language, site-review status, weather telemetry, forecasts, or health guidance.
+- Do NOT change environmental data values.
+- Do NOT restyle the dashboard beyond tiny documentation links if needed.
+- Do NOT add public-health, recreation, regulatory, emergency, or forecast guidance.

README.md

@@ -141,7 +141,13 @@ Run the public mirror validation check from PowerShell:
 powershell -NoProfile -ExecutionPolicy Bypass -File .\scripts\validate-public-mirror.ps1
 ```
 
-If a local server is running on `http://127.0.0.1:4173/`, include endpoint checks:
+Or run the cross-platform Python validation helper:
+
+```bash
+python scripts/validate-public-mirror.py
+```
+
+If a local server is running on `http://127.0.0.1:4173/`, include endpoint checks (PowerShell only):
 
 ```powershell
 powershell -NoProfile -ExecutionPolicy Bypass -File .\scripts\validate-public-mirror.ps1 -CheckHttp

scripts/validate-public-mirror.py

@@ -392,4 +392,4 @@ def main() -> int:
 
 
 if __name__ == "__main__":
-    sys.exit(main())
+    sys.exit(main())