Add Cloudflare Access auth for /internal and harden Sentry config

[sergical]

Summary

• Adds /internal endpoint protected by Cloudflare Access JWT validation (Sentry Google SSO, @sentry.io only)
• /internal uses a shared team Plausible API key — no per-user key needed
• /mcp remains unchanged for direct Bearer token users
• Hardens Sentry config and adds security headers per SEC-1266 review

What changed

• src/worker.ts: two-route architecture — /internal (CF Access JWT) and /mcp (Bearer token)
• src/worker.ts: verifyCloudflareAccessJwt() validates signature via JWKS, audience, expiry, and @sentry.io email
• src/worker.ts: sendDefaultPii: false + beforeSendSpan scrubber for Authorization/cookie headers
• src/worker.ts: Sentry.setUser({ email }) on /internal for attribution on shared key
• src/worker.ts: security headers (X-Frame-Options: DENY, Strict-Transport-Security, Referrer-Policy)
• src/tools/*: manual Sentry spans with tool-specific attributes on each handler
• src/server.ts: uses plain McpServer (tools have their own spans, avoids double error capture)

SEC-1266 review

Reviewed sentry-mcp PRs 164, 485, 625, 930 for hardening patterns. Applied security headers from PR 485. OAuth-specific patterns (consent dialog, HMAC state, redirect URI validation) are not applicable — Cloudflare Access handles the auth flow.

Architecture

Worker (Sentry.withSentry)
├── /internal/*  → CF Access JWT validation → shared PLAUSIBLE_API_KEY
└── /mcp/*       → Bearer token → caller's own API key

Deploy checklist

• Configure Cloudflare Access application for plausible-mcp.sentry.dev/internal/* with Sentry Google SSO IdP
• Set worker secrets: CF_ACCESS_TEAM_DOMAIN, CF_ACCESS_AUD, PLAUSIBLE_API_KEY
• Deploy with bun run deploy
• Verify /mcp Bearer flow still works
• Test /internal with CF Access auth

Test plan

• Build passes (TypeScript compilation)
• All 53 tests pass
• Deploy and test /internal with Cloudflare Access configured
• Verify /mcp direct Bearer flow unaffected
• End-to-end Cowork connector test

🤖 Generated with Claude Code

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