fix(web): add edit and delete experiment functionality (#8)

* feat(web): add parameter and scenario comparison helpers

Add _params_equal() for numeric-tolerant dict comparison and
_scenarios_equal() for effective-parameter comparison that strips
metadata keys and merges global defaults before diffing.

* feat(web): add delete experiment functionality

Add delete_experiment() pure function and show_delete_experiment_dialog()
with confirmation UI. Includes 4 unit tests covering directory deletion,
result file cleanup, and error cases for None/missing paths.

* feat(web): add update experiment with smart result invalidation

Add update_experiment() with 3-tier invalidation strategy:
- No-op: nothing changed, preserve all results
- Targeted: only changed/removed scenarios invalidated
- Full: global parameter changes invalidate all results

Includes _delete_scenario_files(), _invalidate_all_results(), and
_invalidate_changed_scenarios() helpers. Handles directory rename
on name change with collision detection.

11 unit tests cover name/description/parameter changes, no-op
detection, collision errors, and scenario-level invalidation.

* feat(web): add edit experiment modal and header action buttons

Add show_edit_experiment_modal() dialog with pre-filled forms for
name, description, global parameters, and dynamic scenario list.
Reuses network_config_form(), distribution_config_form(), and
simulation_params_form() components with edit-scoped key prefixes.

Modify header layout to [6,4] split with [2,1,1] action sub-columns
for Analyze, Edit, and Delete buttons. Icon-only coloring: green
(Analyze), orange (Edit), red (Delete) with nowrap text.

Includes session state lifecycle management with stale-guard
detection to prevent state leaks on dialog X-close.

Author: mcaxtr