feat: make PR quality verification self-enforcing

Contributors and coding agents need one local command that both reports and enforces the quality contract. This change turns the PR gate into the shared verification entrypoint, adds path-selected local lanes, tightens coverage accounting around changed lines, and documents the repair loop in contributor and agent-facing guidance.

Constraint: Ordinary PR verification must stay non-live and runnable without provider credentials
Constraint: Coverage policy updates in this commit require maintainer approval before push/merge
Rejected: Keep quality guidance only in docs | agents need executable scripts and AGENTS.md instructions to follow the loop consistently
Confidence: high
Scope-risk: broad
Directive: Do not bypass `bun run verify` for production changes; fix failed lanes and coverage reports instead of lowering thresholds
Tested: bun run check:policy
Tested: ALLOW_CLI_CORE_CHANGE=1 ALLOW_COVERAGE_BASELINE_CHANGE=1 bun run verify
Not-tested: live provider baseline; no provider credentials were required for this non-live PR gate

docs/.vitepress/config.mts

@@ -192,6 +192,12 @@ export default withMermaid(defineConfig({
     },
   },
 
+  vite: {
+    build: {
+      chunkSizeWarningLimit: 1800,
+    },
+  },
+
   head: [
     ['script', { async: '', src: 'https://www.googletagmanager.com/gtag/js?id=G-D42DM82263' }],
     ['script', {}, `window.dataLayer = window.dataLayer || [];\nfunction gtag(){dataLayer.push(arguments);}\ngtag('js', new Date());\ngtag('config', 'G-D42DM82263');`],