[quality] Unit tests needed for bluefin-dynamic-wallpaper (hemisphere/month logic)

## Finding `system_files/bluefin/usr/libexec/bluefin-dynamic-wallpaper` contains non-trivial seasonal wallpaper logic: - Southern hemisphere month offset: `(MONTH_NUM + 5) % 12 + 1` - Personal wallpaper detection (regex matching against current gsettings) - Latitude parsing and validation - Error handling for location service failures (exit codes 0, 2, non-zero) - Month padding and wallpaper file existence checks An off-by-one in the month calculation silently delivers the wrong wallpaper for all southern-hemisphere users. The latitude parsing has edge cases around negative numbers and validation. ## Recommendation Add `tests/test_dynamic_wallpaper.bats` testing: 1. Northern hemisphere month→wallpaper mapping (months 1-12) 2. Southern hemisphere offset (month 7 → wallpaper 01, etc.) 3. Personal wallpaper detection (non-bluefin wallpaper → early exit) 4. Invalid latitude handling (non-numeric, empty) 5. Location service failure modes (exit code 2 vs other errors) 6. Missing wallpaper file → exit 1 Mock `gsettings`, `date`, and `/usr/libexec/get-geoclue-latitude` with PATH-based stubs. ## Priority - Impact: **medium** — wrong wallpaper for half the user base if broken - Effort: **low** — straightforward mocking, self-contained logic --- *Filed by quality agent (hold-gated mode)* <!-- factory-pipeline-start --> **Common · issue pipeline** ```text ▶ triage needs kind/ + area/ then /approve · discussing — · queued — · claimed — · done — ``` **area:** — &nbsp; **priority:** — **maintainer:** set kind/ + area/ labels, then comment /approve **reporter:** answer questions; add repro steps if a bug <!-- factory-pipeline-end -->