feat(logging): add Riverpod state observability via ProviderObserver (6/6)

[runyaga]

Summary

• Adds LoggingProviderObserver that pipes all Riverpod state transitions into soliplex_logging at debug level
• Adds Loggers.state logger for the State domain
• Wires observer into ProviderScope in runSoliplexApp
• Includes worktree-safe wrapper scripts for pre-commit hooks (same as PR fix(hooks): add dart fix step and worktree-safe wrappers #234)

Changes

• lib/core/logging/logging_provider_observer.dart: New base class implementing Riverpod 3 ProviderObserver API — logs provider.name: newValue via Loggers.state.debug()
• lib/core/logging/loggers.dart: Add State logger
• lib/run_soliplex_app.dart: Wire LoggingProviderObserver into ProviderScope.observers
• test/core/logging/logging_provider_observer_test.dart: Unit tests for named and unnamed provider logging
• scripts/: Worktree-safe wrapper scripts for dart format and flutter analyze
• .pre-commit-config.yaml: Use wrapper scripts instead of bare commands

Why

Closes the last major observability gap: LLMs (via get_app_logs) and integration tests (via TestLogHarness / MemorySink) can now see all Riverpod state changes alongside HTTP traffic, auth events, and AG-UI lifecycle logs.

Test plan

• flutter analyze — 0 issues
• Unit tests pass (2 tests: named provider, unnamed provider)
• Pre-commit hooks pass (dart format + flutter analyze)