Changes for 0.5.0

[Idleness76]

plethora of changes based on suggestions from production users made for another release before rc.1

Description

• AppRunner::create_iterative_session(...) and AppRunner::invoke_next(...) for repeated graph invocations under one durable session lineage.
• RunnerError::InvalidIterativeEntry for invalid iterative entry nodes.
• Typed state-slot helpers: StateKey<T>, StateSnapshot::get_typed(...), StateSnapshot::require_typed(...), VersionedState::add_typed_extra(...), VersionedStateBuilder::with_typed_extra(...), and NodePartial::with_typed_extra(...).
• Runtime clock injection through RuntimeConfig::with_clock(...), AppRunnerBuilder::clock(...), and NodeContext::now_unix_ms().
• Optional node event metadata for invocation_id and now_unix_ms when runtime metadata is configured.
• INVOCATION_END_SCOPE and AppRunner::finish_iterative_session(...) for long-lived iterative event streams.
• Graph and run metadata helpers: App::graph_metadata(), App::graph_definition_hash(), RuntimeConfig::config_hash(), and AppRunner::run_metadata().
• Reducer::definition_label(...) so graph metadata can distinguish reducer implementations, not only reducer counts.
• Replay conformance helpers in weavegraph::runtimes::replay for normalized event comparison, final-state comparison, and reusable replay assertions.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test improvements

Testing

• Existing tests pass (cargo test)
• Added new tests for changes
• Tested manually (describe how)

Checklist

• My code follows the project's code style (cargo fmt)
• I have run clippy and addressed warnings (cargo clippy)
• I have updated documentation (if needed)
• I have added tests that prove my fix/feature works
• All tests pass locally
• I have updated CHANGELOG.md (if user-facing change)
• I have checked that no breaking changes are introduced (or documented them)