Make UI tests a blocking CI gate (triage 16 pre-existing failures)

[NickCrew]

Description

The ui-tests job in .github/workflows/signal-horizon-quality.yml runs pnpm --filter @atlascrew/signal-horizon-ui test with continue-on-error: true, so UI test failures never block a merge. As of TASK-99 there are 16 pre-existing failing tests across 9 files (TarpitConfig, LoadingStates, ClickHouseOpsPanel, ThreatTrajectoryFeed, PlaybookRunner, CampaignTimelinePage, HuntingPage, DlpConfig, EntityConfig). New tests pass but old breakage accumulates. Triage each failure: fix it, or quarantine with it.skip + a per-failure tracking issue, then drop continue-on-error: true so the job becomes a real gate.

Acceptance Criteria

• Migrate synapse-waf to Rust 2024 edition #1 Each of the 16 pre-existing failing UI tests is either fixed or quarantined with it.skip + a tracking issue
• Cache parsed EvalContext data across body-phase and deferred WAF passes #2 ui-tests job in signal-horizon-quality.yml drops continue-on-error: true and becomes a required check
• Instantiate and integrate HeaderProfiler for per-endpoint header anomaly detection #3 CI fails on any UI test regression
• Escalate invalid-session weight non-linearly to catch faster brute-force #4 Quarantine list (if any) is documented in apps/signal-horizon/ui/CLAUDE.md or a docs/devel/testing/ note

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Migrated from backlog TASK-100 (synapse).