v0.3.0

Breaking

• Error gains GitRecovery and QuotaReserve variants; exhaustive matches
  on Error need a new arm.
• New public fields break struct literals: fetch::issues::IssueData
  (pending_comments, pending_labels, pending_assignees),
  fetch::pull_requests::PullRequestData (node_id, pending,
  changed_files_reported, check_runs_truncated, ...), and
  sync::SyncSummary (partial).

Added

• Nested-connection continuation, so heavy pull requests and issues land with
  every comment, review, thread and file instead of the first slice.
• Git-backed recovery of pull-request file sets GitHub caps at 3,000 files.
• sync targets, sync repair-plan, sync check-history and
  sync check-history-plan.
• GithubDW::open_read_only.
• query::PrFilters and PrState::parse: the filter set the CLI and the MCP
  query tool share.
• MetricsEngine::group_metrics, storage::config_repository, and
  sync_state_repository::{active_syncs, recent_jobs}.

Changed

• query --state with an unknown value now lists the accepted values.
• Internal layout: sync, the CLI binary, check_history and
  fetch::git_files are split into submodules. Public paths are unchanged.