Log per-batch timing info during tome:static for build observability

Problem/Motivation

drush tome:static outputs a progress bar and a final success message, but nothing in between. On large sites a build can run for tens of minutes, processing many recursive batches as related paths are discovered. When a build hangs, slows down, or behaves unexpectedly, there's no log
signal to indicate which batch was running, how big it was, how long it took, or how many related paths it discovered. Operators have to instrument Tome themselves to get any visibility.

This becomes especially relevant when builds run unattended on CI or nightly cron — the only artifact is the final exit code, with no breadcrumbs to point at a slow batch when something goes wrong.

Proposed resolution

Emit two structured log lines per batch in StaticCommand::exportPaths():

• Before the batch runs: [Timer][HH:MM:SS] Starting batch: N paths, M chunks...
• After it completes: [Timer][HH:MM:SS] Batch complete: X.XXs (Y related paths discovered)

The output goes through the existing $this->io->writeln(), so it respects the Symfony Console verbosity layer and shows up in Drush's normal stdout stream alongside the progress bar. Two short lines per batch — minimal noise even on quiet runs, and immediately useful when something goes
wrong.