feat: add terminal and conda activation instructions for pydsm

Author: dwr-psandhu

.github/instructions/terminal-conda.instructions.md

@@ -0,0 +1,44 @@
+---
+description: "Use when running terminal commands in pydsm. Always use Command Prompt (cmd) and always start by activating the dsm2ui conda environment before executing any project commands."
+name: "pydsm Terminal And Conda Activation"
+---
+# Terminal And Environment Rules
+
+- Use Command Prompt (`cmd`) for terminal commands in this repository.
+- The terminal may default to PowerShell. ALWAYS run `cmd` first as a separate step, wait for the prompt, then run `conda activate dsm2ui` as a separate step, wait for activation, then run the project command.
+- Never chain these three steps with `;` or `&&` — run each as its own command.
+- If the environment is unavailable, stop and ask for the correct environment setup instead of continuing in a different shell.
+
+## Standard Command Sequence (three separate steps)
+
+```bat
+cmd
+```
+```bat
+conda activate dsm2ui
+```
+```bat
+<project command here>
+```
+
+## Examples
+
+```bat
+cmd
+```
+```bat
+conda activate dsm2ui
+```
+```bat
+python -m pytest tests/
+```
+
+```bat
+cmd
+```
+```bat
+conda activate dsm2ui
+```
+```bat
+python -c "from pydsm.output.hydroh5 import HydroH5; ..."
+```