chore(fleet): prune ghost files, resync the gitignore fleet block, drop the stale taze patch

Three housekeeping items the current checks surfaced on this base:

- Sixteen untracked ghost files from an older bundle's hydration (the
  removed concurrent-cargo-build-guard hook, .kimi-code, the pre-normalize
  assets/*.svg paths, and seven lib/doc files upstream has since deleted).
  thin-untracks-are-recoverable names them because the current bundle does
  not ship them; each was verified gone from the wheelhouse's template
  before deletion, which is the check's own prescription for stale fleet
  content.
- The .gitignore <fleet-pack> block never pruned: it carried those
  ghosts' entries and missed ~140 current ones. Rewritten from the
  applied-files marker through the check's own isAlwaysTrackedSurface
  predicate (pack-owned = marker minus always-tracked), not by blanket
  copy — the first pass at this ignored 62 tracked files and had to be
  redone.
- patches/taze@19.17.1.patch, stale since the catalog moved to 20.0.0.

Seven pack-shipped paths the previous history re-tracked (the four
assets/fleet SVGs, .config/fleet/.prettierignore + oxlintrc.json, and
test/fleet/_shared/lib/isolate-home-env.mts) leave the index via the
ignored-files check's --untrack; hydration restores them byte-identical.

Author: jdalton