chore(deps): Use stable Agents and MCP SDK releases (#1211)

Switch the Cloudflare Agents and MCP dependencies from preview/beta
builds to their latest stable releases:

- `agents`: preview build → `0.20.1`
- `@modelcontextprotocol/server`: `2.0.0-beta.5` → `2.0.0`
- `@modelcontextprotocol/sdk`: `1.29.0` → `1.30.0`

This also refreshes the pnpm lockfile, including the stable MCP client
transitively required by Agents.

Checks:
- `pnpm install --frozen-lockfile`
- `pnpm run tsc`
- `pnpm run lint`
- `pnpm run test`
- `git diff --check`

Note: `pnpm peers check` reports upstream peer mismatches from Agents
dependencies (`@babel/core`, `rolldown`, `vite`, and
`@cloudflare/workers-types`), but the repo's required typecheck, lint,
and full tests pass.

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Requested by **David Cramer** via Junior.
<!-- junior-request-attribution:end -->

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Co-authored-by: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>
Co-authored-by: David Cramer <david@sentry.io>

Author: sentry-junior[bot]

pnpm-lock.yaml

@@ -17,7 +17,7 @@ allowBuilds:
   workerd: true
 
 overrides:
-  "@modelcontextprotocol/sdk": 1.29.0
+  "@modelcontextprotocol/sdk": 1.30.0
   fast-xml-parser: 5.7.2
   seroval: ^1.5.4
   undici: ^7.24.4
@@ -33,8 +33,8 @@ catalog:
   "@cloudflare/vitest-pool-workers": 0.14.1
   "@cloudflare/workers-oauth-provider": ^0.8.2
   "@cloudflare/workers-types": ^4.20260405.1
-  "@modelcontextprotocol/sdk": 1.29.0
-  "@modelcontextprotocol/server": 2.0.0-beta.5
+  "@modelcontextprotocol/sdk": 1.30.0
+  "@modelcontextprotocol/server": 2.0.0
   "@radix-ui/react-accordion": ^1.2.20
   "@radix-ui/react-slot": ^1.2.3
   "@sentry/cloudflare": 10.54.0
@@ -49,7 +49,7 @@ catalog:
   "@types/react-dom": ^19.1.6
   "@vitejs/plugin-react": ^4.6.0
   "@vitest/coverage-v8": ^4.1.10
-  agents: https://pkg.pr.new/cloudflare/agents/agents@948a90d444759d3f60aa357d72a0c3cedf4aabcb
+  agents: 0.20.1
   ai: ^6.0.64
   better-sqlite3: ^11.10.0
   chalk: ^5.4.1
@@ -89,3 +89,4 @@ minimumReleaseAgeExclude:
   - '@ai-sdk/provider-utils@4.0.40'
   - '@ai-sdk/react@3.0.232'
   - ai@6.0.230
+  - agents@0.20.1