feat(memory): rebuild chat memories by window

[AAswordman]

Summary

• add windowed chat-history memory rebuilding with raw user/assistant messages only
• make extraction output protocol strict named JSON and improve candidate-memory context
• separate selected-chat management and memory rebuilding actions in the history UI

Issue

N/A - implements the requested chat-history memory rebuild workflow.

Compatibility and data

• The previous, unreleased chat-history operation UI is replaced.
• Persisted chat summaries remain excluded from long-term memory extraction.
• No schema migration is introduced.

Validation

• git diff --cached --check`n- XML localization resources were checked during implementation.
• Android build and tests were not run, per repository instruction unless explicitly requested.

Checklist

• Scope is focused on chat-history memory rebuilding.
• User-facing strings are localized.