Make sanitizers CI gate blocking: fix all findings

> [!IMPORTANT]
> Link the implementing PR to this issue by including `Closes #`
> in the PR description or commit message.

### What

Remove `continue-on-error: true` from the `QA / Sanitizers` CI job so that
unresolved sanitizer findings block PR merges.

The flag was added intentionally when the job was introduced because the codebase
had pre-existing sanitizer findings. Once all findings tracked in #76, #77, #78, #79
are fixed, this gate can be made blocking.

### Acceptance Criteria

- [ ] All ASan/UBSan/LSan findings resolved across all components (see #76, #77, #78, #79)
- [ ] `continue-on-error: true` removed from the `sanitizers` job in `.github/workflows/sanitizers.yml`
- [ ] `QA / Sanitizers` CI job passes without findings on a clean branch

### References

- Sanitizers CI job introduced in: #43
- SCA fix tasks (blockers): #76, #77, #78, #79