fix(run): draw the lane console through the canvas renderer

Scrolling a console left stray characters glued to the left edge of blank
lines. Copying an affected line yields clean text, so the buffer was always
correct — only the painting drifted, which no CSS can correct.

xterm's default DOM renderer aligns each row with a single `letter-spacing`
value. That holds only while every glyph comes from one monospace font, and
TerminalView passed no fontFamily, so xterm used its default
`courier-new, courier, monospace`: Vietnamese diacritics and CJK fall
through to a fallback face whose advance width differs, glyphs shove their
neighbours along, and the row's tail spills onto the row below.

The canvas renderer draws every cell at a fixed position, so a wide glyph
can no longer displace its neighbours. Loaded best-effort — a browser that
cannot hand back a 2D context keeps the DOM renderer rather than losing the
terminal entirely.

Ruled out first, each by replaying the real byte stream into xterm.js and
diffing against `tmux capture-pane`: wrapped Vietnamese at the margin, mixed
CJK, wheel scrolling through copy-mode, and a live 131->95->131 resize all
render byte-identically at matched widths.

client 448/448, tsc clean.

client/package-lock.json

@@ -10,6 +10,7 @@
       "dependencies": {
         "@fontsource/inter": "^5.2.8",
         "@fontsource/jetbrains-mono": "^5.2.8",
+        "@xterm/addon-canvas": "^0.7.0",
         "@xterm/addon-fit": "^0.10.0",
         "@xterm/xterm": "^5.5.0",
         "d3": "^7.9.0",
@@ -2073,6 +2074,15 @@
         "url": "https://opencollective.com/vitest"
       }
     },
+    "node_modules/@xterm/addon-canvas": {
+      "version": "0.7.0",
+      "resolved": "https://registry.npmjs.org/@xterm/addon-canvas/-/addon-canvas-0.7.0.tgz",
+      "integrity": "sha512-LF5LYcfvefJuJ7QotNRdRSPc9YASAVDeoT5uyXS/nZshZXjYplGXRECBGiznwvhNL2I8bq1Lf5MzRwstsYQ2Iw==",
+      "license": "MIT",
+      "peerDependencies": {
+        "@xterm/xterm": "^5.0.0"
+      }
+    },
     "node_modules/@xterm/addon-fit": {
       "version": "0.10.0",
       "resolved": "https://registry.npmjs.org/@xterm/addon-fit/-/addon-fit-0.10.0.tgz",