refactor: type navigation pattern context

[chubes4]

Summary

• move Navigation-only evidence and policy callbacks into typed NavigationPatternContext
• replace five mixed fields and five callback getters in generic PatternContext with one typed dependency
• preserve separate normal, runtime-DOM-restricted, and probe context composition

This is the next bounded PatternContext simplification slice from #242. It establishes an explicit Navigation seam without rewriting Navigation's behavior-dense lowering internals.

Stability proof

• 31 brand-anchor hoist assertions
• 41 brand-cue carrier assertions
• 12 staged-dispatch and probe assertions
• reused-transformer session parity
• full canonical and parity suites

Verification

• composer test
• 280 parity fixtures
• package install proof

AI assistance

OpenAI GPT-5.6 Sol via OpenCode was used to trace Navigation-only dependencies, introduce the typed context boundary, preserve normal/restricted/probe policy composition, and run verification. Chris Huber is responsible for every line.