fix: buffer SSE response reads

[Anuja-jayasinghe]

Purpose

This draft fixes the HTTP client's poor performance when reading large SSE events.

getSseEventStream currently requests one-byte chunks and performs one stream read for every byte while looking for the SSE event delimiter. This makes a 2 MB SSE event take several seconds even though the same data as a unary response is read in well under a second.

The change uses the normal buffered response stream and retains unread bytes locally. The parser still handles fragmented input and delimiters split across chunks, including one-byte chunks, without forcing every read to be one byte.

Examples

The repository's existing hostile-server s_huge case sends a 2,000,000-byte artifact in one SSE event. The same server also exposes the payload as u_huge in a unary response.

Path	Measured time
Existing SSE reader	6.89–8.24 s
Buffered SSE reader	0.49–0.52 s
Unary response	0.41–0.49 s

The buffered reader returned the complete payload: 2,000,000 artifact bytes and 2,000,476 bytes including SSE framing. An integration test also covers a 64 KiB SSE event and verifies that the payload is not truncated.

Checklist

• Linked to an issue — repository issues are disabled; no upstream issue was filed
• Updated the changelog — pending maintainer direction for this draft
• Added tests — large SSE event integration coverage
• Updated the spec — not applicable; this is an implementation/performance fix
• Checked native-image compatibility — not run locally
• Checked the impact on OpenAPI generation — not applicable to the SSE reader

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud