feat(testing): add conftest sys.path config and clean unused imports [ticket-031]

[MatthiasLew]

Adds tests/conftest.py for automated pytest sys.path resolution and cleans unused imports across application files.

[ifuri-validator-agent]

Deterministic Validator approval for exact head 4ff8ca9c817cd30f8869668683b87b5161e00bbc.

Ticket: ticket-031
Correlation ID: data2dsl-pr-31-ticket-031
Model: openrouter/z-ai/glm-5.2
Reviewed diff chunks: 1
Advisory LLM verdict: APPROVE
Advisory summary: Reviewed all 1 diff chunk(s). Ticket 031 adds tests/conftest.py for automatic pytest sys.path resolution and removes genuinely unused imports from src/data2dsl_cli.py, src/data2dsl_skill.py, and tests/test_golden_case_e2e.py. The changes are scoped, non-behavioral, and match the stated intent. Governance gate passed.
Advisory findings: none
The LLM output above is advisory and was not used as the approval trust root.
Merge will be attempted after this approval when explicitly authorized.

Decision record (recomputable)

DECISION D-031-8363
TICKET ticket-031
HEAD_SHA 4ff8ca9c817cd30f8869668683b87b5161e00bbc
CORRELATION_ID data2dsl-pr-31-ticket-031
ACTOR agent:ifuri-validator-agent[bot]
APPLIED_RULE P-CORE-015
INPUT author_login = "MatthiasLew"
INPUT observed_checks = ["governance / remote lifecycle=PASS"]
INPUT required_checks = ["governance / remote lifecycle"]
INPUT required_checks_source = "protected registry + GitHub applied rules (env/request)"
INPUT reviewer_login = "ifuri-validator-agent[bot]"
VERDICT APPROVE AUTHORITY DETERMINISTIC
REJECTED REQUEST_CHANGES BECAUSE NO_UNSAFE_CHANGE_REASON_FOUND
ADVISORY llm_verdict = "APPROVE" MODEL "openrouter/z-ai/glm-5.2"
ASSERT VERDICT_AUTHORITY != "ADVISORY"