docs: add ADR for ratcheted CodeScene thresholds (guard — from commit 311dcc64)

docs/adr/0018-codescene-code-health-gates.md

@@ -2,8 +2,9 @@
 type: ADR
 id: "0018"
 title: "CodeScene code health gates in CI and git hooks"
-status: active
+status: superseded
 date: 2026-03-13
+superseded_by: "0064"
 ---
 
 ## Context

docs/adr/0064-ratcheted-codescene-thresholds.md

@@ -0,0 +1,30 @@
+---
+type: ADR
+id: "0064"
+title: "Ratcheted CodeScene thresholds as the quality gate baseline"
+status: active
+date: 2026-04-14
+---
+
+## Context
+
+ADR-0018 established CodeScene code-health gates so Tolaria could block regressions before code reached `main`. Since then, the codebase has improved materially and the tracked baseline in `.codescene-thresholds` has been ratcheted above the original 9.50 / 9.31 minimums.
+
+Leaving ADR-0018 active would make the architecture record stale: the enforced thresholds are now stricter than the decision document says, and the current workflow intentionally tightens them as the project's sustained health improves.
+
+## Decision
+
+**Supersede ADR-0018 and treat `.codescene-thresholds` as the ratcheted policy baseline for Tolaria's CodeScene gate.** The current required minimums are `HOTSPOT_THRESHOLD=9.84` and `AVERAGE_THRESHOLD=9.45`. Thresholds move upward only when the repository can sustain a stricter baseline without immediately regressing.
+
+## Options considered
+
+- **Ratchet the enforced thresholds and document the new baseline** (chosen): keeps the ADRs aligned with the real gate, preserves the Boy Scout Rule, and makes code-health expectations stricter as the codebase improves.
+- **Keep ADR-0018 active and treat higher thresholds as an implementation detail**: lower documentation churn, but the active ADR would no longer describe the actual CI and hook policy.
+- **Remove numeric thresholds from ADRs entirely**: more durable on paper, but loses the explicit quality bar that developers are expected to maintain.
+
+## Consequences
+
+- `.codescene-thresholds` is now the authoritative location for the current numeric gate values.
+- ADRs must be superseded again if Tolaria makes another meaningful policy jump in CodeScene thresholds.
+- Pre-push and related quality checks now enforce a stricter floor than ADR-0018 described.
+- The quality gate remains intentionally one-way: relaxing thresholds would require an explicit architectural reversal, not a quiet config edit.

docs/adr/README.md

@@ -73,7 +73,7 @@ proposed → active → superseded
 | [0015](0015-auto-save-with-debounce.md) | Auto-save with 500ms debounce | active |
 | [0016](0016-sentry-posthog-telemetry.md) | Sentry + PostHog telemetry with consent | active |
 | [0017](canary-release-channel-and-local-feature-flags.md) | Canary release channel and feature flags | superseded → [0057](0057-alpha-stable-release-channels-and-beta-cohorts.md) |
-| [0018](0018-codescene-code-health-gates.md) | CodeScene code health gates in CI | active |
+| [0018](0018-codescene-code-health-gates.md) | CodeScene code health gates in CI | superseded → [0064](0064-ratcheted-codescene-thresholds.md) |
 | [0019](0019-github-device-flow-oauth.md) | GitHub device flow OAuth for vault sync | superseded → [0056](0056-system-git-cli-auth-no-provider-oauth.md) |
 | [0020](0020-keyboard-first-design.md) | Keyboard-first design principle | active |
 | [0021](0021-push-to-main-workflow.md) | Push directly to main (no PRs) | active |
@@ -119,3 +119,4 @@ proposed → active → superseded
 | [0061](0061-ai-prompt-bridge-event-bus.md) | AI prompt bridge — module-level event bus for cross-component prompt routing | active |
 | [0062](0062-selectable-cli-ai-agents.md) | Selectable CLI AI agents with a shared panel architecture | active |
 | [0063](0063-blocknote-code-block-package-for-editor-highlighting.md) | BlockNote code-block package for editor syntax highlighting | active |
+| [0064](0064-ratcheted-codescene-thresholds.md) | Ratcheted CodeScene thresholds as the quality gate baseline | active |