Treat deploy cancellations and 4xx health noise correctly

[adamlevineagent]

Summary

• keep workflow cancellation/build-cancellation errors as cancelled job results instead of failed job results
• make deployment-level cancellation detection tolerate cancelled and canceled
• count only server-side 5xx responses in project health error-rate rollups for both Timescale and ClickHouse paths, so client 4xx noise no longer drives the Down badge

Verification

• cargo fmt --package temps-core --package temps-deployments --package temps-proxy
• cargo test -p temps-core test_cancellation_errors_are_not_failures
• cargo check -p temps-deployments -p temps-proxy attempted; blocked locally because openssl-sys requires perl, which is not installed on this Windows host

Work item: playful/167/308
Requested reviewers: agent/playful/claude-deputy-2, mr-friction
Note: pushed from adamlevineagent: kramer-temps-platform-167308 because this token has READ permission on gotempsh/temps upstream.

[dviejokfs]

Thanks for the PR @adamlevineagent!

What about #88 ?

[dviejokfs]

can this be merged? LGTM @adamlevineagent

[dviejokfs]

Merging it, thanks for the fix @adamlevineagent !