test(recorded): add client cassette coverage (3/5)

[Pouyanpi]

Summary

Adds recorded client-level coverage for OpenAI chat and embeddings flows.

Why

Client cassette smoke tests validate that the harness can replay basic provider traffic before the rails API coverage layers on top.

What Changed

• Adds OpenAI chat cassette coverage.
• Adds OpenAI embeddings cassette coverage.
• Adds minimal configs used by the client tests.

Stack Position

Part 3 of 5.

• Previous: fix(llmrails): load library files deterministically (2/5) #1975
• Next: test(recorded): add rails public API coverage (4/5) #1977

Stack Context

This stack decomposes recorded end-to-end replay coverage into reviewable slices. The PRs should be reviewed against their parent branch in the stack.

Please review each PR against its parent branch, not directly against the root base branch, except for part 1.

Order	PR	Branch	Base
1	#1974	stack/recorded-tests-01-harness	develop
2	#1975	stack/recorded-tests-02-deterministic-library-load	stack/recorded-tests-01-harness
3	#1976	stack/recorded-tests-03-clients	stack/recorded-tests-02-deterministic-library-load
4	#1977	stack/recorded-tests-04-public-api	stack/recorded-tests-03-clients
5	#1978	stack/recorded-tests-05-library-rails	stack/recorded-tests-04-public-api

Validation

poetry check --lock
poetry lock --no-update
poetry install --with dev
poetry run pytest tests/recorded --block-network -q
pre-commit hooks passed during commit creation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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