Add lnav.org feature

[Copilot]

Adds a devcontainer feature for lnav — an advanced terminal log file viewer with multi-file support, automatic format detection, and syntax highlighting.

Changes

• src/lnav.org/ — New feature using the gh release install method. Downloads the Linux musl static zip from tstack/lnav releases, extracts the binary via unzip -p, and places it at /usr/local/bin/lnav. Architecture mapping: amd64→x86_64, arm64→arm64.
• test/lnav.org/test.sh — Smoke test: lnav --version
• README.md — Added lnav.org row in alphabetically sorted feature table

Asset naming (tstack/lnav releases)

lnav-{version}-linux-musl-x86_64.zip   # amd64
lnav-{version}-linux-musl-arm64.zip    # arm64

Zip contains binary at lnav-{version}/lnav; extracted with unzip -p piped directly to the target path.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add "lnav.org" feature</issue_title>
<issue_description>Gh repo tstack/lnav</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add "lnav.org" feature #191

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