fix: preserve registry recursion fallbacks

[chubes4]

Summary

• route Accordion, Disclosure, and Navigation brand-carrier recursion through PatternRecursiveConverter
• preserve recursive fallback diagnostics transactionally with the winning pattern result
• remove three parallel recursion callbacks from PatternContext and three fallback-discarding HtmlTransformer wrappers
• keep Navigation probe contexts recursion-free

Closes #919. This is the next bounded PatternContext simplification slice from #242.

Behavior proof

• Accordion and Disclosure retain html_unsupported_element evidence from valid panels containing unsupported children
• Navigation retains recursive brand diagnostics only when the brand carrier wins
• Navigation probe context performs no recursive conversions
• excluded-tag conversion preserves fallback ordering through the typed converter

Verification

• composer test on current trunk
• 12 staged-dispatch assertions
• 280 parity fixtures
• package install proof

AI assistance

OpenAI GPT-5.6 Sol via OpenCode was used to trace the remaining fallback-discarding recursion paths, consolidate them into the typed converter, add transactional behavior coverage, rebase onto current trunk, and run verification. Chris Huber is responsible for every line.