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/server/package.json

@@ -53,10 +53,6 @@
       "types": "./dist/types/api.d.ts",
       "default": "./dist/types/api.js"
     },
-    "./ws-frames": {
-      "types": "./dist/types/ws-frames.d.ts",
-      "default": "./dist/types/ws-frames.js"
-    },
     "./db": {
       "types": "./dist/db.d.ts",
       "default": "./dist/db.js"
@@ -81,6 +77,7 @@
     "test": "vitest run"
   },
   "dependencies": {
+    "@boocode/contracts": "workspace:*",
     "@ai-sdk/openai-compatible": "^2.0.47",
     "@fastify/static": "^7.0.4",
     "@fastify/websocket": "^10.0.1",