[r3dbars]

Fix

Fixes #2250. Builds on #2218. Validate each owned per-run directory component before descending/creating it; reject symlinked reports/logs and escaping run/state identifiers before cleanup, writes or launch. Preserve concurrent-run isolation and the explicit output root's supported canonical alias.

Evidence

• Independent full repair review against original Isolate Sparkle smoke launch reports per run #2218 head: no blocking finding.
• Focused Sparkle package suite: 9 tests PASS, independently rerun.
• Deliberately restoring the unsafe guard makes two regressions fail with five assertions; restoring the repair returns all nine tests green.
• Synthetic fake apps and test-owned temporary directories only; no real app, capture, settings or publication.
• Static guards and diff check PASS. Final combined gates and applicable exact-head CI are pending; remains draft until complete.

This is bounded harness containment, not a claim of race-free behavior under a hostile concurrent filesystem swap. Native account-isolation guard remains unchanged.

[r3dbars]

Final review: the complete repair diff was independently approved, its original defect reproduced, and its regression tests passed. Exact repair-head CI is green. Combined candidate 75488fb passed mapped checks, fresh full deterministic QA/build and safe synthetic paste verification; see #2255 for evidence and the explicit native, thin-packaging and release limitations. Ready for the owner-authorized ancestry-preserving integration; no release or live hardware clearance is implied.