Terminal supports pixel-precision (fine) mouse tracking via SGR-Pixels mode

What

• Pointer handling for press, drag, release, and hover throughout the terminal renderer now threads a fine boolean alongside button/column/row, to distinguish precise trackpad input from coarse mouse clicks, along with a raw fractional position on mouse events.
• The terminal capability prober now sends a DECRQM query for mode 1016 (SGR-pixel mouse coordinates) plus a cell-size query, so Claude Code can detect whether the terminal supports pixel-level mouse reporting.
• New machinery, including retainFinePointer/cancelFinePointerSettle hold-counting, syncMousePixels, and mouseReportsInPixels, turns the terminal's mousePixels mode on and off as needed, with a "fine pointer settle" timer managed on mount and unmount.
• New helpers translate mouse column/row into pixel-precise coordinates when supported, and the mousePixels mode is reasserted on redraw alongside the existing extendedKeys and mouse modes.
• New regexes and a MOUSE_SGR_PIXELS constant parse the SGR-Pixels escape sequences and convert pixel offsets into row/column plus the fine payload.

Why

On terminals that support it, this lets interactive elements in Claude Code respond to precise trackpad or mouse positioning rather than only whole character cells, enabling finer-grained interactions.