fix(web): add edit and delete experiment functionality

[mcaxtr]

Summary

Adds full edit and delete capabilities to the experiment detail page, complementing the existing scenario-level edit/delete that was already in place.

• Edit experiment: modal dialog with pre-filled forms for name, description, global parameters, and dynamic scenario list
• Delete experiment: confirmation dialog that removes the entire experiment directory
• Smart result invalidation: 3-tier strategy preserves results when possible, only invalidating what actually changed
• Header redesign: action bar now includes Edit, Delete, and Analyze buttons in a balanced layout

Changes

Comparison helpers

• _params_equal() — numeric-tolerant dict comparison (handles int/float mismatch from JSON deserialization)
• _scenarios_equal() — compares effective parameters (globals + overrides), strips metadata keys like status

Delete experiment

• delete_experiment() — pure function, validates path exists, calls shutil.rmtree()
• show_delete_experiment_dialog() — @st.dialog with confirmation message, warning, and Cancel/Delete buttons

Update experiment with smart invalidation

• update_experiment() — core update with 3-tier invalidation:
  • No-op: nothing changed -> preserve all results
  • Targeted: only changed/removed scenarios -> invalidate those scenario results only
  • Full: global parameter changes -> invalidate all scenario results + experiment analysis
• _delete_scenario_files(), _invalidate_all_results(), _invalidate_changed_scenarios() helpers
• Directory rename on name change with collision detection

Edit experiment modal

• show_edit_experiment_modal() — @st.dialog("Edit Experiment", width="large")
• Pre-seeds session state with current experiment values via _init_edit_experiment_state()
• Reuses network_config_form(), distribution_config_form(), simulation_params_form() with edit_exp_* key prefixes
• Dynamic scenario list with add/remove/render matching creation modal patterns
• Session state lifecycle management with stale-guard detection (prevents leaks on dialog X-close)

Header layout

• Changed from [8, 2] to [6, 4] column split
• Three sub-columns: Edit (:material/edit:), Delete (:material/delete:), Analyze (existing)

Test coverage

15 new tests (22 total in file):

Class	Tests	Coverage
TestDeleteExperiment	4	Directory deletion, result file cleanup, None path error, non-existent dir error
TestUpdateExperiment	11	Name/description/param changes, no-op detection, name collision, empty name, normalized rename, scenario removal, scenario override change, empty scenarios, duplicate labels

Diff stats

spkmc/web/pages/experiment_detail.py     | 795 ++-
tests/test_web/test_experiment_detail.py | 498 ++
2 files changed, 1279 insertions(+), 14 deletions(-)

Test plan

• All 22 unit tests pass (pytest tests/test_web/test_experiment_detail.py -v)
• Full suite passes (pytest — 468 passed, 19 skipped)
• Manual: Edit experiment name -> directory renames, results preserved
• Manual: Edit global params -> all results invalidated
• Manual: Delete experiment -> returns to dashboard
• Manual: X-close edit dialog -> no stale state on reopen