fix(observability): render skipped pipeline steps

[GuddXzy]

Scope

Scope boundary: Render the documented skipped-by-gate pipeline step state as SKIPPED in read-only replay transcripts, while preserving existing OK and FAIL(<reason>) output.

Non-goals: Change pipeline execution, decision-log persistence/schema, other replay fields, or unrelated CLI output.

Branch

Base branch: main

Target exception: N/A

Issue

Linked issue: Fixes #1503

If None, reason: N/A

Release Note

Release note: Replay transcripts now distinguish conditionally skipped pipeline steps from failures.

Tests

Ruff: uv run ruff check src tests — passed

Pytest:

• uv run pytest -q tests/test_observability/test_replay.py tests/test_observability/test_decision_log_contract.py — 7 passed
• uv run pytest -q tests/test_observability — 193 passed, 1 skipped
• Full-suite local Windows attempt — could not complete reliably because of unrelated platform E2E behavior; the first deterministic blocker under pytest -vv -x was a functional gateway SQLite disk I/O error in test_real_gateway_suppresses_goal_sentinel_everywhere after 351 passed and 8 skipped. Upstream CI provides the repository's sharded Ubuntu and selected Windows coverage.

Build:

• npm --prefix opensquilla-webui run build — passed
• uv build --wheel — passed

Regression tests: added

Notes: The regression matrix covers OK, SKIPPED, FAIL(boom), and an empty failure reason rendered as FAIL(). The implementation intentionally checks fallback_reason is None rather than truthiness.

The default test path remains offline, deterministic, credential-free, and safe for forks.

Maintainer Live Check

Maintainer live check: no

Surface: N/A

Maintainer-only note: no credentialed live check is needed for the read-only replay formatter.

Safety

No secrets, local-only artifacts, private prompts/transcripts, channel identifiers, AI session artifacts, non-public fixtures, or tests/_private/ contents are included.

Third-Party Origin

Third-party origin: none

Details if non-none: N/A

Documentation Changes

No documentation changes. The existing pipeline contract already names this state skipped-by-gate; this PR corrects the renderer to match it.

• Links point to existing repository files or stable external pages.
• Code fences and Markdown tables render correctly on GitHub.
• Examples avoid real secrets, local private paths, and private transcripts.

[GuddXzy]

Thanks for the focused fix and regression tests. I checked the current main branch, and skipped steps are still rendered as FAIL(None), so #1503 remains unresolved.

CI, PR body lint, and PR target branch currently show action_required, with no CI jobs executed. Could a maintainer check whether these workflows need approval and review this PR? The branch is also behind main; please advise whether an update is needed before validation.