feat: pi-devbox parity — typst PDF, terminal terminfo, nvim colour, host-ssh check, hygiene

Ports the base additions from pi-devbox v1.4.0 + v1.5.0 that opencode-devbox
lacked (opencode-devbox already tracks pi-devbox for CLI-toolset parity, v2.6.0):

- typst PDF engine for pandoc (v1.4.0) + the pandoc typst-template default-font
  patch (v1.5.0) so 'pandoc --pdf-engine=typst' works without -V mainfont.
  pandoc shipped since v2.6.0 as a front-end only (no PDF back-end). +xz-utils.
  Tracks latest; --build-arg TYPST_VERSION escape hatch.
- Terminal support (v1.5.0): ncurses-term + kitty-terminfo + a compiled
  xterm-ghostty alias (tic -x, use=ghostty), so wezterm/alacritty/foot/ghostty/
  kitty resolve TERM over SSH instead of degrading to a dumb fallback.
- Readable Neovim colours (v1.5.0): system-wide /etc/xdg/nvim/sysinit.vim with
  termguicolors.
- Host SSH reachability check at shell startup (v1.4.0): one-time probe in
  .bash_aliases warning (with fix steps + inline pubkey) when the Mac host is
  unreachable. The rest of the LAN stack was already present.
- .claude/settings.local.json added to the gitignore_global seed (v1.5.0).
- Repo hygiene (v1.5.0): LICENSE (MIT), THIRD_PARTY.md, hadolint CI job (pinned
  v2.14.0) + .hadolint.yaml, IDEAS.md backlog.

Base-affecting (Dockerfile.base + rootfs) → base-<hash> advances, base rebuilds.
smoke-test gains typst/PDF, terminfo, and nvim-tgc assertions. Validated:
hadolint clean on both Dockerfiles, bash -n OK, base-hash guard OK, workflow
guard OK. CHANGELOG v2.7.0.

.gitea/workflows/lint.yml

@@ -66,3 +66,27 @@ jobs:
         # ("no project was found"). Globbing the workflow files is the
         # supported way to lint a non-GitHub layout.
         run: actionlint -color .gitea/workflows/*.yml
+
+  hadolint:
+    # Lint the two Dockerfiles that ARE the project (the shell/actions linting
+    # above never looked at them). Config — ignored rules + failure threshold
+    # — lives in .hadolint.yaml, which hadolint reads automatically, so a local
+    # `hadolint Dockerfile.base` reproduces CI exactly.
+    runs-on: ubuntu-latest
+    container:
+      image: catthehacker/ubuntu:act-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install hadolint (pinned)
+        env:
+          HADOLINT_VERSION: 2.14.0
+        run: |
+          curl -fsSL \
+            "https://github.com/hadolint/hadolint/releases/download/v${HADOLINT_VERSION}/hadolint-Linux-x86_64" \
+            -o /usr/local/bin/hadolint
+          chmod +x /usr/local/bin/hadolint
+          hadolint --version
+
+      - name: Run hadolint
+        run: hadolint Dockerfile.base Dockerfile.variant