feat: single-source cross-app wire contracts in @boocode/contracts (v2.7.13)

Move all hand-synced cross-app wire contracts into one built workspace
package, @boocode/contracts, consumed by server/web/coder/coder-web via
workspace:* + a per-subpath exports map. The ws-frames and provider-config
Zod schemas are schema-first (z.infer); MessageMetadata, ErrorReason,
AgentSessionConfig, the provider snapshot types, and WorktreeRiskReport are
each single-sourced. Deletes the byte-identical copies and their parity
tests, fixes a live AgentSessionConfig drift (coder dead copy removed,
unified to the web required/nullable shape), removes the dead pending_change
WS arms in the fallback SPA, and inverts the build order (contracts builds
first) across root build, Dockerfile, and the coder deploy docs. Reverses
the shared-package decision declined in v2.5.12.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/web/src/hooks/useSessionStream.ts

@@ -1,7 +1,7 @@
 import { useEffect, useRef, useState } from 'react';
 import { toast } from 'sonner';
 import type { Message, WsFrame } from '@/api/types';
-import { WsFrameSchema } from '@/api/ws-frames';
+import { WsFrameSchema } from '@boocode/contracts/ws-frames';
 import { api } from '@/api/client';
 import { sessionEvents } from './sessionEvents';
 import { recordUsage } from './useChatThroughput';