refactor: extract PaginationCoordinator and RowEditingCoordinator

[datlechin]

Summary

Phase 4 step 4. Two more focused coordinators extracted from MainContentCoordinator's 5 extension files (~903 LOC moved). Same pattern as PR #1125 (FilterCoordinator + QueryExecutionCoordinator). State stays on tabManager.tabs and is mutated via the mutate(tabId:) API from PR #1124.

Extracted

PaginationCoordinator (Core/Coordinators/PaginationCoordinator.swift, 221 LOC)

• Combines methods from +Pagination.swift (~77 LOC) + +LoadMore.swift (~150 LOC).
• 1 Task closure, captures [weak self, parent] (avoids the dangling-unowned-parent bug PR refactor: extract FilterCoordinator and QueryExecutionCoordinator #1125 had to follow up).

RowEditingCoordinator (Core/Coordinators/, 3 files, 682 LOC)

• Main file (241 LOC) plus +SaveChanges.swift (314 LOC) and +Discard.swift (127 LOC).
• Split into extension files because combined would cross the 1100-line type_body warning.
• 4 Task closures, all capture [weak self, parent] or [parent].

Forwarders

22 thin forwarders kept on existing extension files so views and tests compile unchanged:

• 7 in +Pagination.swift, 2 in +LoadMore.swift (cancelCurrentQuery, fetchAllRows)
• 10 in +RowOperations.swift, 1 in +SaveChanges.swift (saveChanges with inout), 2 in +Discard.swift

Out of scope

• MainContentCoordinator+TabSwitch.swift (audit score -10, undo manager coupling). Stays for now.
• Central query entry points (runQuery, executeQueryInternal, etc.) stay on MainContentCoordinator.
• assemblePendingStatements and fkEnableStatements stay on parent — RowEditingCoordinator+SaveChanges accesses via parent.X. Tests reference them directly, not in scope to relocate.

Verification

• xcodebuild Debug builds (BUILD SUCCEEDED).
• swiftlint clean across all 7 touched files.
• All 5 Task closures verified: grep -nE "Task \\{|Task\\(" TablePro/Core/Coordinators/Pagination*.swift TablePro/Core/Coordinators/RowEditing*.swift shows every Task uses [parent] capture.
• Pre-existing test failure in TableProTests/Core/Storage/QueryHistoryManagerTests.swift (type 'NSNotification.Name?' has no member 'queryHistoryDidUpdate') is unrelated to this refactor — file unchanged vs main.

Commits

1. 6f193e9 - extract PaginationCoordinator
2. 501dca5 - extract RowEditingCoordinator (with SaveChanges + Discard sub-files)

Test plan

• Build clean (verified)
• Pagination: next/prev page, page size change, total row count populates
• Load More: fetch all rows on a paginated table, observe progress
• Cancel an in-flight COUNT(*) or fetch-all
• Insert row, edit cell, delete row, save changes, verify SQL preview
• Discard pending changes, verify undo state cleared
• FK toggle on save (truncate + re-enable order preserved)