fix(mcp): recover expired HTTP sessions

[mattzcarey]

Summary

Recover a streamable HTTP MCP connection when the server returns HTTP 404 for a session restored from storage.

The client now:

• identifies HTTP 404 only while probing a restored streamable HTTP session;
• clears that session id from memory and durable storage;
• initializes a fresh session and rediscovers capabilities once.

Application-level JSON-RPC errors with code 404 are unchanged, as are failures on sessions negotiated in the current lifetime.

Why this is needed

The MCP SDK skips initialize when given a persisted session id. If the server expires that session while the Agent sleeps, restore appears connected but discovery remains wedged on 404 across later wakes.

The regression still reproduces on current main; the new session-lifecycle test fails there and passes with this fix.

Validation

• pnpm --filter agents exec vitest run src/tests/mcp — 30 files, 548 tests passed
• focused package lint and TypeScript checks passed
• pnpm run check passes through exports, formatting, lint, and packages/agents typechecks; repo-wide typecheck is currently blocked by unchanged main voice errors in examples/voice-agent and voice-providers/assemblyai

Includes a patch changeset for agents.

[changeset-bot]

🦋 Changeset detected

Latest commit: be0bdce

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
agents	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

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commit: be0bdce