test: address actionable tier 2 refactors from issue 478

[mariusvniekerk]

Summary

• extract shared helpers in review command tests
• move log rendering coverage into internal/streamfmt and add typed stream event builders
• share fix-job and storage fixture helpers across daemon and storage tests
• leave the older ci_poller_test.go tier 2 item alone because it no longer maps cleanly to the current code

Commits

• 7af09ff test: extract review command helpers
• 0b9775d test: move log rendering tests into streamfmt
• 68ecd1b test: use typed stream formatter events
• 73f27b4 test: share fix job test helpers
• 7b7f67f test: add db job test fixture helper
• 6f0f1bd test: extract migration fixture schemas

Test Plan

• go fmt ./...
• go vet ./...
• go test ./...

Related to #478.

[roborev-ci]

roborev: Combined Review (6f0f1bd)

Verdict: All reviewers agree the code is clean and no issues were found in these test-only refactors.

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Synthesized from 3 reviews (agents: codex, gemini | types: default, security)