Document the jig release packages and fix the go install module path

[miharp]

Closes #482

The Installing Jig section only described the release tarballs and go install. Since v2.3.0 every jig release also ships .deb and .rpm packages, a Windows zip, and sha256sums.txt.

Changes to docs/_ecosystem_8x/devkit/jig.md:

• List what each release ships (packages, archives, checksum file).
• New Linux packages subsection that installs straight from the GitHub release URL: VERSION and BASE variables, then curl -LO plus apt install ./jig_${VERSION}_linux_amd64.deb for Debian/Ubuntu, and dnf install ${BASE}/jig_${VERSION}_linux_amd64.rpm for the Red Hat family (dnf accepts URLs; apt does not). The BASE variable keeps each command line inside the code block's visible width instead of scrolling. Notes the binary lands in /usr/bin and that there is no apt/dnf repository, so upgrades are the same steps with the next version.
• Archives subsection keeps the existing unpack-and-move instructions, adds a shasum -a 256 -c --ignore-missing sha256sums.txt check, and reworded the macOS Gatekeeper tip to say "macOS binaries" rather than "packages".
• Go subsection corrects the command to go install github.com/voxpupuli/jig/v2@latest. jig's go.mod is github.com/voxpupuli/jig/v2 and the v1 tags still exist, so the old command resolves @latest to v1.5.0.

Verification:

• Ran both go install forms locally: the un-suffixed one produces a binary reporting jig@v1.5.0 (no --version flag); the /v2 one reports jig version v2.4.0.
• Inspected jig_2.4.0_linux_amd64.deb: contains /usr/bin/jig and /usr/share/doc/jig/LICENSE.
• shasum -a 256 -c --ignore-missing sha256sums.txt verifies the downloaded deb on macOS.
• Ran the Debian block verbatim (VERSION, BASE, curl -LO): the deb matches sha256sums.txt, and the rpm URL built the same way returns 200. The releases/latest/download/ shortcut does not work because the asset names include the version.
• markdownlint-cli2 clean (new list uses * to match the file's existing bullet style).
• Built the site and checked the rendered section at 1440px and 400px: the three h3s appear in the page outline, and no command line overflows the code block.

Upstream jig's own install docs have the same gap; tracked at voxpupuli/jig#96.

The page says there is no apt or dnf repository for jig. That is true today, but OpenVoxProject/openvox-release-infra#24 is building a tools component for the Go tools (jig, g10k, webhook-go, openvox-ca, openvoxview, gorge). The tools-release packages and .repo files are already on apt.voxpupuli.org and yum.voxpupuli.org, but the repository itself is still empty (the yum tools/ baseurl returns 404 and there is no tools component under the apt dists). Once packages land there, this section should switch to recommending the repository over the standalone downloads.

Assisted by Claude.