Always show review explanations

[VIVAAN-DHAWAN]

Summary

Follow-up to #11: this carries the final explanation and logo-polish changes that were pushed after #11 was merged.

• Always creates an explanation when the reviewer opts in.
  • Uses the configured AI provider when available.
  • Falls back to a clearly labelled local explanation from Diffly’s deterministic facts when there is no AI key or the provider fails.
• Reuses an authenticated gh session for private-repository access and higher GitHub API limits.
• Removes the unintended white highlight lines from the refreshed logo.

Verification

• python -m pytest -q — 50 passed
• python -m compileall -q src
• git diff --check

[github-actions]

Diffly verdict: QUARANTINE

#12 · 6 files · 188 lines changed · checks: PENDING

Risk flags: NO_TEST_COVERAGE (medium), CHECKS_PENDING (low)

Risk flags and reasoning

• NO_TEST_COVERAGE (medium): Changed production files have no obvious neighboring or repository test coverage. — assets/logo-v2.svg; src/diffly_cli/cli.py; src/diffly_cli/github.py
• CHECKS_PENDING (low): Required status checks are still pending. — combined commit status; diffly; test (3.10); test (3.12); test (3.13)
• QUARANTINE because at least one changed production file lacks obvious test coverage.
• QUARANTINE because required checks are still running.

Blast-radius summary

File	Change	Symbols	Direct callers	Tests
assets/logo-v2.svg	+0/-5	—	—	—
src/diffly_cli/cli.py	+33/-21	render_explanation	—	—
src/diffly_cli/explainer.py	+67/-3	local_explanation	local_explanation	tests/test_explainer.py, tests/test_explainer.py
src/diffly_cli/github.py	+23/-1	__init__, github_auth_token	github_auth_token	—
tests/test_explainer.py	+7/-5	<top-level changes>	—	—
tests/test_regressions.py	+20/-3	<top-level changes>	—	—

Deterministic triage is authoritative; any optional LLM explanation cannot change the verdict.