Upgrade go-sdk to v1.6.0 and consolidate session-missing detection

[Copilot]

This module is the core MCP dependency in gh-aw-mcpg, and the repo was one minor version behind on modelcontextprotocol/go-sdk. This PR updates the SDK and tightens a small MCP transport code path called out in the review by removing duplicated session-not-found string matching.

• Dependency refresh

  • Bumps github.com/modelcontextprotocol/go-sdk from v1.5.0 to v1.6.0.
  • Updates transitive module metadata/checksums (including github.com/google/jsonschema-go).

• Session-not-found detection cleanup

  • Introduces a shared constant for the backend session-missing message in internal/mcp/http_transport.go.
  • Reuses that constant in both helpers:
    • isSessionNotFoundError
    • isSessionNotFoundHTTPResponse
  • Keeps behavior unchanged while removing duplicated literals.

• SDK contract annotation update

  • Updates the bypass-validation contract note in internal/server/tool_registry.go to reflect verification against go-sdk v1.6.0.

const (
    HTTPTransportPlainJSON HTTPTransportType = "plain-json"
    sessionNotFoundMessage                   = "session not found"
)

func isSessionNotFoundError(err error) bool {
    if errors.Is(err, sdk.ErrSessionMissing) {
        return true
    }
    return strings.Contains(strings.ToLower(err.Error()), sessionNotFoundMessage)
}

[lpcox]

@copilot fix the failing linting ci check

[Copilot]

Pull request overview

Updates the repository’s core MCP dependency (modelcontextprotocol/go-sdk) to v1.6.0 and slightly refactors the HTTP transport session-missing detection to remove duplicated string literals, while also updating one SDK-contract annotation.

Changes:

• Bump github.com/modelcontextprotocol/go-sdk from v1.5.0 to v1.6.0 (and refresh transitive sums, incl. github.com/google/jsonschema-go).
• Consolidate "session not found" matching into a shared constant in internal/mcp/http_transport.go.
• Update the bypass-validation SDK behavior note in internal/server/tool_registry.go to reference v1.6.0 verification.

Show a summary per file

File	Description
internal/server/tool_registry.go	Updates the SDK-contract verification comment to v1.6.0.
internal/mcp/http_transport.go	Introduces sessionNotFoundMessage constant and reuses it in both session-missing detectors.
go.mod	Upgrades go-sdk to v1.6.0 and bumps jsonschema-go indirect dependency.
go.sum	Refreshes checksums for upgraded direct/transitive modules.

Copilot's findings

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• Files reviewed: 3/4 changed files
• Comments generated: 1

[lpcox]

@copilot address the review feedback

[Copilot]

@copilot fix the failing linting ci check

Fixed in the latest commit. The staticcheck rule SA9004 flagged mixing typed (HTTPTransportType) and untyped constants in the same const block. I moved sessionNotFoundMessage into its own separate const declaration to resolve it.

[Copilot]

@copilot address the review feedback

Done. Updated all three stale v1.5.0 annotation occurrences to v1.6.0 in http_transport.go, connection.go, and http_transport_test.go.