fix(console): fix canvas scrollbar gutter, scroll redraw, and mobile spacing

[SandipGhimire]

Issue

• Extra blank line at the bottom: term.writeln() appended \r\n after every line and left the cursor visible on a trailing empty row, creating extra gap above the command input.
• Overridden / clipped text when scrolling:
  • Ghostty's default measureFont() only measured "M", whose near-zero descent caused descenders (g, j, p, q, y, [, ]) to bleed across rows and not clear cleanly during scroll redraws.
  • Empty/null scrollback rows were skipped during redraws instead of clearing their row background, leaving stale text behind.
  • Terminal.resize() in ghostty-web overwrote canvas.width without devicePixelRatio scaling, and FitAddon's 50ms _isResizing lock dropped immediate post-layout and mobile ResizeObserver re-fits.
• Mobile layout & resize overflow: Negative mobile margins (-ml-4 w-[calc(100%+2rem)]) pushed the console outside the page container past the power buttons, and missing min-w-0 / overflow-hidden prevented the flex wrapper from shrinking when resizing down to mobile.

Solution

• Eliminate trailing blank row: Prefix \r\n before subsequent writeln calls instead of after the last line, hide the read-only canvas cursor (cursorVisible = false), and remove bottom container padding when the command input is visible.
• Clean scroll & resize rendering:
  • Measure full glyph ascent and descent (measureTerminalFont) so rows never clip or overlap descenders.
  • Return [] instead of null from getLine / getScrollbackLine, clamp viewportY to [0, maxScrollback], and clear the canvas background whenever the whole-line viewport shifts.
  • Unlock FitAddon's _isResizing guard (unlockFitResize) and preserve HiDPI canvas sizing in term.resize().
• Fix mobile alignment: Use w-full, min-w-0, and overflow-hidden on the console containers in Console.tsx so the terminal and ConsoleScrollbar align and resize properly on mobile viewports.