0.20.0 agent-efficiency and simplification pass

[zackbart]

Goal

Ship a breaking 0.20 release that reduces agent routing mistakes, context cost, and maintenance burden while keeping the two deployment shapes and fail-closed execution boundary intact.

Release PRs

• Remove direct-call field projection and qualify large-result retrieval #482 remove direct field projection and add large-document qualification
• Reduce program UI to display-only output #484 reduce program UI to display-only output
• Replace named legacy config refusals with strict unknown-key validation #485 strict configuration validation
• Keep generated operator UI declarations below 1 KB #486 generated declaration size
• Move the copied UI credential-deployment helpers into test/fixtures/ui.ts #479 remaining UI fixture deduplication

Measured exclusions

• Reject conversational-only and weak single-term discovery matches #481 discovery negatives: the candidate failed its sealed qualification run, so draft PR Reject conversational-only and weak partial discovery matches #491 does not enter 0.20
• Measure host support for lean object-result encoding #483 lean object-result encoding: the host matrix failed and Cursor was unavailable, so the issue closed with no product change

Follow-up evidence, not 0.20 blockers

• Make the agent routing gate pinned, powered, and uncontaminated #496 pinned, statistically powered, uncontaminated routing gate
• Measure persisted catalog cost on cold Worker isolates #487 persisted catalog cost on cold Worker isolates
• Declare useful outputs for Cloudflare's schema-silent named tools #488 Cloudflare output quality before provider growth
• Design a maintained Mixpanel export/activity-feed connection for per-user event timelines #432 remains deferred while the provider freeze holds

Release gate

Every merged behavior change has an independent review. Main passes npm run release:check, npm run test:browser, the current-version audit, the 52 KB direct-paging agent case, and the final agent routing lane compared with the preserved untouched-main control. A fresh connecta init deployment passes connecta doctor; Docker smoke runs when Docker is available. Package version, template pin, upgrade guide, and changelog move together in the final release PR. Publishing and tagging are separate operator actions.

[zackbart]

Release operator explicitly waived the credentialed hosted-MCP catalog half of npm run drift:check because the four local maintainer credentials were unavailable. The published-spec half was fully reviewed, recorded in #505, and rerun clean. All other 0.20.0 gates passed.