refactor: eliminate 4 cross-package duplicate-code patterns (server/proxy)

[Copilot]

Four structural duplication patterns across internal/server and internal/proxy were causing diverging implementations that silently drift as the codebase evolves.

Pattern 1 — newSDKServer helper (internal/server/http_server.go)

Extracted the repeated sdk.NewServer(&sdk.Implementation{...}, &sdk.ServerOptions{...}) block into a shared helper used by both routed.go and unified.go. Removed now-unused version imports from both files.

func newSDKServer(name string, log *logger.Logger) *sdk.Server {
    return sdk.NewServer(&sdk.Implementation{
        Name:    name,
        Version: version.Get(),
    }, &sdk.ServerOptions{
        Logger: logger.NewSlogLoggerWithHandler(log),
    })
}

Pattern 2 — Standardized DIFC parse-error warning (internal/proxy/proxy.go)

Replaced logProxy.Printf("WARNING: ...") with logger.LogWarn("startup", ...) to match the logging style already used in server/unified.go.

Pattern 3 — Shared health/reflect response helpers (internal/httputil/endpoint_helpers.go)

Added WriteSimpleHealthResponse(w) and WriteReflectResponse(w, difcComponents) to httputil — the package both server and proxy already import. The proxy's inline /health and /reflect branches now call these helpers; server/reflect.go does too. This ensures both packages route through identical code as difc.BuildReflectResponse evolves.

Pattern 4 — toResultOrWriteEmpty method (internal/proxy/handler.go)

Extracted the two identical Phase-5 ToResult failure blocks into a single method on proxyHandler:

func (h *proxyHandler) toResultOrWriteEmpty(w, resp, responseData, labeled) (interface{}, bool)

Returns (result, true) on success; logs, writes an empty-shaped response, and returns (nil, false) on error so the caller can return cleanly.

[lpcox]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in commit 8e584792. The only conflict was a single import line in internal/server/routed.go: our branch removed version (moved to http_server.go via newSDKServer) while main's #7170 refactor removed strutil (moved to session_util.go via a local truncateSessionID wrapper). The correct resolution is to drop both imports — the merged file uses neither directly. All tests pass.

[Copilot]

Pull request overview

This PR refactors repeated logic across internal/server and internal/proxy to reduce drift between “unified” vs “routed” server modes and proxy endpoints, by centralizing common server construction, endpoint responses, and DIFC result handling.

Changes:

• Consolidates MCP SDK server creation into a shared newSDKServer helper used by both unified and routed server modes.
• Standardizes proxy DIFC parse-error warnings via logger.LogWarn(...) to match existing startup logging patterns.
• Extracts shared /health and /reflect response helpers into internal/httputil and reuses them from both server and proxy.
• Removes duplicated Phase-5 ToResult error handling by introducing toResultOrWriteEmpty in the proxy handler.

Show a summary per file

File	Description
internal/server/unified.go	Switches MCP SDK server construction to the shared newSDKServer helper.
internal/server/routed.go	Switches routed per-backend MCP SDK server construction to newSDKServer.
internal/server/reflect.go	Reuses shared httputil.WriteReflectResponse for consistent reflect output.
internal/server/http_server.go	Adds newSDKServer helper and centralizes version/logger wiring for MCP SDK server creation.
internal/proxy/proxy.go	Uses logger.LogWarn for DIFC parse warnings to align with unified server logging style.
internal/proxy/handler.go	Extracts duplicated ToResult failure handling; uses shared health/reflect response helpers.
internal/httputil/endpoint_helpers.go	Adds shared health and reflect response helpers used by both server and proxy.

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• Files reviewed: 7/7 changed files
• Comments generated: 0