docs(lemonade): use Launchpad PPA for Linux install + fix v10.2.0 navbar label

[kovtcharov]

Summary

The version pin itself already landed in #865 (which bundled a 10.0.0 → 10.2.0 bump alongside a 100-file feature PR). After merging main, this PR is now scoped to the three loose ends #865 didn't fix:

• cpp/README.md + docs/cpp/setup.mdx — switch Linux install from a lemonade-server_10.2.0_amd64.deb curl (which 404s — Lemonade dropped the .deb asset in v10.0.1+) to the Launchpad PPA flow upstream now recommends.
• docs/docs.json — navbar label still said "Lemonade 10.0.0" after feat(llm): add Gemma 4 E4B as default and native tool_calls priority #865; bumping to match the actual pin.

Net delta vs main: 3 files, +13/-13 lines. Verified with python util/check_doc_versions.py (all references consistent) and pytest tests/unit/test_lemonade_version_check.py tests/unit/test_init_command.py (73 passed).

Follow-up

#815 still open — src/gaia/installer/lemonade_installer.py builds the same dead .deb URL inside gaia init and needs a similar PPA-based refactor. That's a behavioural change to a CLI command (different blast radius from a docs swap) so it's tracked separately.

Test plan

• python util/check_doc_versions.py → consistent
• pytest tests/unit/test_lemonade_version_check.py tests/unit/test_init_command.py → 73 passed
• Manual sanity check on Mintlify preview that the navbar shows "v0.17.4 · Lemonade 10.2.0"

[github-actions]

Summary

Clean, tightly-scoped dependency bump of LEMONADE_VERSION from 10.0.0 → 10.2.0. The single source of truth (src/gaia/version.py:12) drives both CI (build-installers.yml:233 parses it to build the MSI URL) and the NSIS installer, so the pin change propagates correctly without workflow edits. Doc updates are consistent: python util/check_doc_versions.py passes locally against this branch, and the Linux install instructions are correctly rewritten to use ppa:lemonade-team/stable since the upstream .deb asset was dropped in v10.0.1.

The single most important thing: the author already called out that src/gaia/installer/lemonade_installer.py:258 still points at the 404ing .deb URL for Linux gaia init, and has deferred it to #815. This is a reasonable scope call for a pure version bump, but it does mean gaia init on Linux will be broken on main between this merge and #815 landing — worth making sure #815 is prioritized.

Issues Found

🟢 Minor — Release-notes example is frozen at an older pin (docs/releases/index.mdx:88)

The release instructions template still shows the navbar label example as "v0.17.0 · Lemonade 10.0.0". It's illustrative ("here's what the field you'll edit looks like") rather than a live claim, so check_doc_versions.py rightly ignores it. Optional refresh for consistency:

        "label": "v0.17.2 · Lemonade 10.2.0",

Skip if you'd rather keep the example stable across releases — either choice is defensible.

🟢 Minor — Stale comment in lemonade_installer.py:256

# Note: v10.0.0+ changed naming from lemonade_ to lemonade-server_

Still technically accurate, but once #815 switches Linux to the PPA flow this code path (and its comment) likely disappears entirely. No action needed in this PR — flagged only so it's on the #815 checklist.

Strengths

• Single source of truth honored: only version.py is the pin; CI (build-installers.yml:238) and NSIS both derive from it, so there's no version drift to chase across workflows.
• Linux instructions fixed, not just bumped: switching to the Launchpad PPA is the right call given Lemonade dropped the .deb release asset after v10.0.1 — without this, the "Or download directly" link would lead users to a page missing the artifact the instructions reference.
• Scope discipline: the lemonade_installer.py Linux path is a behavioural change (download-and-dpkg → add-apt-repository + apt install) and deserves its own PR/Linux gaia init downloads nonexistent Lemonade .deb (v10.0.1+) #815. Bundling it here would have turned a clean bump into a reviewable behavioural change.
• Test plan is concrete: references the two suites that actually guard this (test_lemonade_version_check.py, test_init_command.py) plus the doc-version checker. That's the right set.

Verdict

Approve. Ready to merge as-is. The docs/releases/index.mdx example label is optional polish, not a blocker. Recommend prioritizing #815 soon after this lands so Linux gaia init isn't broken on main for long.

[kovtcharov]

@claude double check the new version of lemonade does not break our current version of Gaia. Point out any new features in lemonade v10.2.0 that we may want to integrate and confirm we have issues for those.