Add branch merge history commands

[adamziel]

What it does

Adds forkpress branch history and forkpress branch tree as focused ways to inspect merge run history. Both commands show source -> target edges with the existing decision and conflict counts.

Also adds --records runs to the lower-level COW merge audit command for automation.

Rationale

Reviewing conflicts was possible through merge-audit, but seeing merge history required knowing the full audit command or cloning the Git mirror. This gives users a direct command for the question “what merged where?” while keeping the deeper audit commands available.

Implementation

forkpress branch history and forkpress branch tree route through the existing merge-audit machinery with records=runs, scope=all, and no conflict filters.

The PHP audit backend now accepts --records runs and rejects incompatible filters the same way it does for rollback/crash-only record sets.

Testing instructions

php -l scripts/cow/merge.php
php -l tests/cow/stale_audit.php
php tests/cow/stale_audit.php
cargo fmt --check
FORKPRESS_RUNTIME_BUNDLE=/dev/null cargo test -p forkpress-cli branch_history -- --nocapture
FORKPRESS_RUNTIME_BUNDLE=/dev/null cargo test -p forkpress-cli branch_help_lists_review_revalidation_command -- --nocapture