fix(macos): seed missing Chobby rapid repository order

[Dimaris-nsk]

When RapidTagResolutionOrder is missing, the bundled Chobby selects the old
repos.springrts.com path for its lobby-version backup. With the current list
under repos-cdn.beyondallreason.dev, that backup is skipped. A controlled list
update then leaves the lobby tag pointing to a version that is not installed.
With the official repository order, the existing Chobby handler restores the
original list and installed lobby tag.

This adds 15 lines to packaging/launcher.sh, based on
562fe461f8b045f863089815edac7f2d6559e178. After merging bundled defaults,
seed repos-cdn.beyondallreason.dev;repos.beyondallreason.dev only when the
complete key is absent. Existing entries, including empty/custom values and
whitespace, remain unchanged. Read or append errors stop through the existing
error helper. No Chobby or engine code is changed.

Validation:

• Six portable Chobby cases, 12 configuration cases with 13 executions of the
  exact shell block, three integrations using the resulting setting, and shell
  syntax validation. All expected outcomes passed.
• In real v0.15.1 Chobby test-4630-26b5200, the original configuration reproduced
  the missing cache. The candidate restored the exact original 146201-byte gzip
  and native installed tag after a controlled incoming-list update and completion
  through the genuine handler callback.
• The fixed client entered a real short BAR test-31251-0ceadc7 game and returned
  to the same menu. Codex agents inspected native and physical window captures;
  both original and fixed runs ended normally with engine exit 0.

Evidence, screenshots and reproducible offline checks.
The native test used direct engine startup with configuration produced by the
exact launcher blocks and a local transport adapter. It does not establish a
real network download, complete Finder/launcher update, account login or public
match. Remaining game/driver warnings are documented in the evidence and are
not claimed to be fixed here.

This does not recover an interrupted update in a fresh Lua instance/process.
The engine may remove explicit empty defaults on a later launch. OpenAI Codex
authored the change, tests and explanation and performed the visual checks;
human review is requested through this PR. The account owner is not represented
as having independently reviewed or tested the code.