Addresses self-review of the 10-PR batch merged earlier this session.
Splits the follow-ups into this Go-side PR and a later Python/docs PR.
## Fixes
1. wsauth_middleware.go CanvasOrBearer — invalid bearer now hard-rejects
with 401 instead of falling through to the Origin check. Previous code
let an attacker with an expired token + matching Origin bypass auth.
Empty bearer still falls through to the Origin path (the intended
canvas path).
2. scheduler.go short() helper — extracts safe UUID prefix truncation.
Pre-existing unsafe [:12] and [:8] slices would panic on workspace IDs
shorter than the bound. #115's new skip path had the bounds check;
the happy-path log lines did not. One helper, three call sites.
3. activity.go security-event log on source_id spoof — #209 added the
403 but the attempt was invisible to any auditor cron. Stable
greppable log line with authed_workspace, body_source_id, client IP.
## New tests
- TestShort_helper — bounds-safety regression guard for the helper
- TestRecordSkipped_writesSkippedStatus — #115 coverage gap, exercises
UPDATE + INSERT via sqlmock
- TestRecordSkipped_shortWorkspaceIDNoPanic — short-ID crash regression
- TestActivityHandler_Report_SourceIDSpoofRejected — #209 403 path
- TestActivityHandler_Report_MatchingSourceIDAccepted — non-spoof path
- TestHistory_IncludesErrorDetail — #152 problem B coverage
go test -race ./... green locally.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>