Fix streamable HTTP SSE exhaustion

[pradeep-ramola]

Fixes #2098

Summary

Updates StreamableHTTPClientTransport so the standalone GET SSE channel does not silently become unusable after reconnect exhaustion.

This change:

• raises the default Streamable HTTP SSE reconnection retry count from 2 to 10
• records when the standalone GET SSE stream exhausts reconnect attempts
• fails subsequent sends immediately with a clear error instead of POSTing into a dead response channel
• preserves existing per-request stream exhaustion behavior via onRequestStreamEnd
• includes response text in failed SSE-open errors when statusText is empty

Testing

• corepack pnpm --filter @modelcontextprotocol/client exec vitest run test/client/streamableHttp.test.ts
• corepack pnpm --filter @modelcontextprotocol/client typecheck
• corepack pnpm --filter @modelcontextprotocol/client build
• corepack pnpm --filter @modelcontextprotocol/client exec prettier --ignore-path ../../.prettierignore --check src/client/streamableHttp.ts test/client/streamableHttp.test.ts
• corepack pnpm --filter @modelcontextprotocol/client exec eslint src/client/streamableHttp.ts

[changeset-bot]

🦋 Changeset detected

Latest commit: 152a73a

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

This PR includes changesets to release 6 packages

Name	Type
@modelcontextprotocol/client	Patch
@modelcontextprotocol/core	Patch
@modelcontextprotocol/server	Patch
@modelcontextprotocol/server-legacy	Patch
@modelcontextprotocol/codemod	Patch
@modelcontextprotocol/core-internal	Patch

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commit: 152a73a

[knoal]

Reviewing via MCE A/B pilot 10 (sophia@hermes.local).

Summary

Fix streamable HTTP SSE exhaustion. 197 LOC, 3 files. Changes the default maxRetries from 2 to 10, suggesting the reconnection logic needed more attempts before giving up. Throws a clear error when a request is sent after the stream is exhausted.

APPROVE — real fix for SSE reconnection logic. The default of 2 retries was too aggressive for flaky networks; 10 is more appropriate.

— sophia