* refactor(matrix): adopt core claimable dedupe for inbound events
* fix(matrix): migrate legacy inbound dedupe markers via doctor
* fix(matrix): single-pool dedupe namespace and capacity-aware legacy import
* fix(matrix): keep unreadable legacy dedupe JSON in place during doctor import
Move Matrix sync cache state into plugin SQLite storage, with startup and doctor migrations for readable legacy bot-storage.json files.\n\nVerification: focused Matrix and QA tests passed locally; focused touched-file oxlint and git diff --check passed; autoreview clean. CI failures are current main/unrelated: lint/type/madge/gateway-watch issues outside the Matrix diff.