Add target-aware differential coverage summaries

[decofe]

Summary

• tag showmap trials with target labels before differential coverage analysis and emit by_target/<name> rows
• extend differential_coverage_summary.csv with monitoring statistics, effect size, CI, decision, and budget columns while preserving existing columns
• add differential_coverage_sequential_state.json with a machine-readable scheduling directive for continue/eliminate/inconclusive decisions
• disable automated winner decisions until the analysis can prove independent seed/round campaign units and use true anytime-valid inference
• scope Holm correction to the top-level per-target family; combined/by-test rows keep their local p-values
• remove fake adaptive savings, fake next seed directives, and the legacy point-estimate winner backdoor

Tests

• uv run --with-requirements analysis/requirements.txt python -m unittest analysis.tests.test_differential_coverage
• git diff --check

Prompted by: @0xalpharush