Add manual workflow_dispatch workflow for running experiments

[Copilot]

This PR adds a dedicated GitHub Actions manual trigger for experiment execution. It enables on-demand runs from the Actions UI for either a single experiment or the full experiment suite.

• What changed

  • Added a new workflow: .github/workflows/experiments-dispatch.yml
  • Introduced workflow_dispatch input experiment as a constrained choice list:
    • all
    • exp_001_dfrc_pareto_frontier through exp_009_5g_vs_6g_full_stack
  • Implemented run logic:
    • all → executes all experiment examples sequentially
    • specific value → executes only the selected example

• Security posture

  • Scoped workflow token permissions to least privilege:
    • permissions: { contents: read }

• Operational impact

  • Provides a single, explicit manual entry point for experiment runs without coupling to push/PR path filters.
  • Supports targeted reruns for one experiment and broad reruns for the whole set from the same workflow.

on:
  workflow_dispatch:
    inputs:
      experiment:
        type: choice
        options:
          - all
          - exp_001_dfrc_pareto_frontier
          # ...
          - exp_009_5g_vs_6g_full_stack

jobs:
  run-experiments:
    permissions:
      contents: read
    steps:
      - name: Run experiment(s)
        run: |
          if [ "${{ github.event.inputs.experiment }}" = "all" ]; then
            # run exp_001..exp_009
          else
            cargo run --example "${{ github.event.inputs.experiment }}"
          fi