fix(pager): keep Git colors in non-diff output for captured pager hosts

[DanielCarmingham]

Fixes #702.

Captured pager hosts like LazyGit advertise TERM=dumb while rendering ANSI in their own panel. Hunk already knows this for diffs — isCapturedPagerHost is what routes those hosts to the static colored renderer instead of launching the TUI. Non-diff input returns passthrough before reaching that check, and passthrough stripped SGR unconditionally, so LazyGit's branch log rendered in a single color.

This reuses that same predicate rather than adding a second heuristic: the fact that already tells the diff path "this host renders ANSI" now also decides whether passthrough preserves it.

const passthroughPlan = {
  kind: "passthrough" as const,
  text: stdinText,
  preserveColor: capturedPagerHost,
};

#381 fixed the same symptom for interactive terminals via pagePlainText, but captured hosts never reach pagePlainText — TERM=dumb sends them down passthrough first.

Before / after

released 0.18.0	this branch

Same repo, same commit, same terminal size — only the pager binary differs.

Verification

• bun run typecheck clean; bun test shows an identical failure set to main on the same base (no regressions, +2 new passing tests)
• Reverting only the source change while keeping the new tests fails 5 of them, so the tests do detect the fix
• Real git log --graph --color=always through hunk pager: 0 → 468 escape sequences under a LazyGit environment, and still 0 for a plain TERM=dumb terminal, so genuinely dumb terminals are unaffected
• Confirmed end to end by driving real LazyGit 0.64.0 in a PTY (screenshots above)

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