Wire crates/zeph-context/src/typed_page.rs into the context summarization
pipeline. Previously the module was fully tested in isolation but had no
integration points and was dead code in production.

Changes:
- zeph-config: add TypedPagesConfig under [memory.compression.typed_pages]
  with enabled/enforcement/audit_sink/flush_timeout_ms fields; disabled by default
- zeph-context: add BatchViolation, BatchAssertions, TypedPagesState; fix
  CompactionAuditSink::flush() with oneshot rendezvous + 100ms timeout cap;
  fix panic on audit_channel_capacity=0 (capacity.max(1)); fix UTF-8 boundary
  panic in body truncation (char-boundary-safe loop)
- zeph-agent-context: add typed_pages field to ContextSummarizationView;
  wire classify step (2.5), SystemContext pointer-replace in active mode (3.5),
  BatchAssertions check (5.5), and audit emit (7.5) into compact_context();
  skip LLM call when entire batch is pointer-replaced SystemContext stubs
- zeph-core: add typed_pages_state to CompressionState and CompactionAdapters;
  expose with_typed_pages_state() builder method
- src/runner.rs: add build_typed_pages_state() async init; wire into builder chain

The feature is zero-cost when disabled. Two regression tests added:
audit_sink_capacity_zero_does_not_panic and
classify_with_role_non_ascii_body_does_not_panic.

Closes #3630