Support incremental page object generation

Problem

When utam-java is consumed via the compiler plugin in a downstream project, every mvn invocation triggers an all-or-nothing rebuild of every page object. google-java-format dominates the cost, so iterative dev loops pay the full formatting bill even when only one .utam.json source has changed.

Proposal

Add an opt-in incremental mode to the compiler that skips generation for page objects whose generated .java artifacts are already newer than their source .utam.json. This preserves current default behavior while giving downstream consumers a large speedup on repeated builds.

Suggested shape

• A CLI flag (e.g. --incremental / -I) and matching JsonCompilerConfig parameter.
• A TranslatorTargetConfig.isUpToDate(...) hook so custom target configs can opt in.
• DefaultTargetConfiguration implements the check via per-page-object mtime comparison: regenerate iff any expected target is missing or older than the source.
• DefaultTranslatorRunner.write() consults the hook before invoking getGeneratedCode() (where the formatter runs) and skips per-PO writes for up-to-date page objects. Aggregate outputs (manifest, DI config) still include every PO.

Linked PR

#243

Start by reviewing linked PR #243, then trace DefaultTranslatorRunner.write(), TranslatorTargetConfig.isUpToDate(...), DefaultTargetConfiguration, and JsonCompilerConfig. Verify the CLI option and configuration reach the runner, up-to-date page objects skip getGeneratedCode(), missing or older targets regenerate, and aggregate outputs still include every page object.