feat(datagrid): copy column values plus Copy as CSV/Markdown/IN Clause (#1325)

[datlechin]

Summary

Closes #1325 (能否添加复制多条id功能? — "Can you add a feature to copy multiple IDs, or copy an entire column?").

Adds two complementary entry points to the data grid:

• Right-click column header → Copy Column Values — copies every value from the loaded rows of the clicked column, one per line. Operates on the currently visible page (matches every other copy action in the app).
• Row context menu → Copy as submenu: new entries for CSV, CSV with Headers, Markdown table, and IN Clause. IN Clause produces (1, 2, 3) or ('a', 'b') from the right-clicked column across the selected rows, ready to paste into a WHERE col IN (...) query.

Native macOS pattern throughout — NSMenu / NSMenuItem with representedObject carrying column indices, dispatching to coordinator methods that mirror the existing copyRowsAsJson(at:) / copyRowsAsInsert(at:) shape. No new abstractions; new converters (CsvRowConverter, MarkdownTableConverter, InClauseConverter) live in Core/Utilities/SQL/ alongside the existing JsonRowConverter / SQLRowToStatementConverter and follow the same struct shape.

ClipboardService gains a writeCsv(_:) method that writes .string + utf8PlainText + public.comma-separated-values-text so pasting CSV into Numbers/Excel works without content-sniffing. writeText and writeRows are unchanged.

Design decisions

• Column Values lives on the column header context menu, not the row Copy-as submenu. HIG-wise headers are for structural actions (sort, hide, resize) and Numbers/Mail follow that pattern. But here the action is self-explanatory and discoverable, similar to TablePlus's "Copy All Column Value". One menu item, no submenu.
• IN Clause uses the right-clicked column, same idiom as the existing "Cell Value" entry. Reflects the user's natural mental model when copy-pasting from a specific cell into a WHERE clause.
• Scope is loaded rows only, not "all matching rows in the database". Matches every other copy operation in the app. No background queries, no surprise costs.
• NULL handling differs by format on purpose — CSV: empty field (RFC 4180 / Postgres COPY default). Markdown: NULL literal (matches grid display). IN Clause: NULLs are filtered out — WHERE x IN (.., NULL, ..) never matches NULL rows in three-valued SQL logic anyway, so emitting them would silently mislead the user.
• No new keyboard shortcuts. Cmd+C (TSV) and Cmd+Shift+C (TSV with Headers) stay default. Cmd+Opt+C is reserved by macOS for "Copy Style" in text contexts and would conflict in the SQL editor.

Code centralization

Following the existing copyRowsAsJson(at:) pattern exactly:

// TableViewCoordinator extension (DataGridView+RowActions.swift)
func copyRowsAsCsv(at:includeHeaders:)
func copyRowsAsMarkdown(at:)
func copyRowsAsInClause(at:columnIndex:)
func copyColumnValues(columnIndex:)

All three converters use the driver-provided escapeStringLiteral closure when the column needs SQL quoting — same pattern as SQLRowToStatementConverter.

Files changed

• New converters: CsvRowConverter.swift, MarkdownTableConverter.swift, InClauseConverter.swift
• New tests: CsvRowConverterTests, MarkdownTableConverterTests, InClauseConverterTests (24 tests, all passing)
• ClipboardService.swift — new writeCsv(_:) plus protocol method; existing mocks updated
• DataGridRowView.swift — 4 new menu items + actions, dedup helper selectedOrCurrentIndices(in:) covering 8 existing call sites that had the same guard/ternary pattern duplicated
• DataGridView+Sort.swift — 1 new header-menu item + action
• Localizable.xcstrings — Xcode auto-extracted new String(localized:) keys
• docs/features/data-grid.mdx — full Copy as / Copy Column Values table, plus a correction (Cmd+Shift+C was documented as "CSV"; it's actually TSV with Headers)

Verification

• 24 new converter tests pass; all existing copy/paste tests in RowOperationsManagerCopyTests + CellPasteRoutingTests still green
• Build clean against the main TablePro scheme
• No banned filler words in CHANGELOG / docs / PR body

Test plan

• Right-click a column header on a SELECT result, choose Copy Column Values, paste into a text editor — one value per line, length matches loaded rows.
• Select 3 rows on an id INT column, right-click on the id cell, Copy as → IN Clause — clipboard contains (1, 2, 3).
• Same flow with a name VARCHAR column — clipboard contains ('a', 'b', 'c') with proper quoting.
• Copy as → CSV with a row containing O'Brien and doe, john — RFC 4180 compliant quoting.
• Copy as → Markdown — pipe-escaped cells render correctly when pasted into GitHub/Discord.
• Existing Cmd+C (TSV) and Cmd+Shift+C (TSV with Headers) behavior unchanged.