feat: parallelize hadolint execution across Containerfiles

Summary

HadolintSuite.run() (posit-bakery/posit_bakery/plugins/builtin/hadolint/suite.py) groups hadolint commands by unique Containerfile, then runs subprocess.run(...) serially in a for loop — one lint invocation per unique Containerfile. This is a straightforward candidate for the tool-agnostic posit_bakery/parallel/ module (ParallelShellExecutor/ShellTask) introduced in #588 for parallel dgoss execution.

Scope

• Port HadolintSuite.run() to build ShellTasks from the grouped HadolintCommands and dispatch through ParallelShellExecutor, following the pattern in plugins/builtin/dgoss/suite.py.
• Add a --jobs/-j flag to the hadolint lint command, matching the dgoss run --jobs convention (BAKERY_MAX_CONCURRENCY env / SETTINGS.max_concurrency, default 4).
• Preserve existing per-Containerfile report/result-file writing and error aggregation (BakeryHadolintError, BakeryToolRuntimeErrorGroup) exactly as-is; only the dispatch mechanism changes.
• Update/extend the live progress table behavior to match dgoss (auto-disable on non-TTY/CI/--quiet/single-task runs).

Out of scope

• Changing hadolint's actual lint rules or output format.

Part of the investigation started in #584. See #588 for the reference implementation pattern (dgoss).

Start with posit_bakery/plugins/builtin/hadolint/suite.py, then read posit_bakery/plugins/builtin/dgoss/suite.py and the posit_bakery/parallel/ module, especially ParallelShellExecutor and ShellTask. Run the hadolint lint command to inspect current behavior; done means grouped Containerfiles execute with configurable --jobs/-j concurrency while report writing, error aggregation, and dgoss-aligned progress behavior remain unchanged.