fix(terminal): quote the sh -c payload so resume survives spaces in paths

[graydawnc]

What

Fixes shell-quoting in the open --args terminal runners (Ghostty / kitty / Alacritty / WezTerm) so the resume command survives cwds and commands that contain spaces or single quotes.

Depends on #405 (stacked — this branch bases on feat/terminal-ghostty). Merge #405 first.

Why

Each runner wrapped the sh -c payload in raw single quotes:

open -a kitty --args sh -c '<payload>'

But withCwd already single-quotes the cwd (cd '<cwd>' && …) and the resume command single-quotes the session id. The nested single quotes cancel out under the outer shell, so it only works when nothing contains a space. A common macOS project path like /Users/x/My Project tokenizes into:

sh -c argument = "cd /Users/x/My"    (+ stray args "Project", "&&", "claude"…)

so sh -c cd just cd's to $HOME and exits — the resume command is dropped and the window opens in the wrong directory (and never runs exec $SHELL).

How it connects

• Extracts keepAliveArg(cmd, cwd), which shell-quotes the entire "<cmd>; exec $SHELL" payload as one token, and routes all four open --args runners through it. This also removes the fourth byte-for-byte copy of the runner template.
• The AppleScript runners (Terminal.app / iTerm2) are untouched — they have a separate quoting model and are out of scope here.

Test plan

• New regression tests tokenize each emitted command with a real /bin/sh and assert the payload survives as a single argument, for both a spaced cwd (/tmp/My Proj) and an embedded single quote. These fail on the pre-fix runners (the spaced path splits into two argv tokens) and pass after.
• Existing Ghostty string assertions updated to the correctly-escaped form.
• Full app vitest suite green (290 tests).