refactor: extract generic listMCPItems helper for list* MCP operations

[lpcox]

Summary

Extracts a generic listMCPItems helper that eliminates the structural duplication across listTools, listResources, and listPrompts in internal/mcp/connection.go.

Problem

The three list functions shared identical boilerplate (~17 lines each):

1. requireSession() check
2. Debug log
3. paginateAll() call with a type-specific fetch closure
4. Error check
5. marshalToResponse() with a type-specific result wrapper

If the list-operation contract ever changes (e.g., new error handling, retry logic, metrics), all three functions had to be updated in sync.

Solution

A new generic listMCPItems[Item, Result] helper centralizes the shared boilerplate. Each list method now delegates to it with only the type-specific SDK calls:

func (c *Connection) listTools() (*Response, error) {
    return listMCPItems(c, "tools",
        func(cursor string) (paginatedPage[*sdk.Tool], error) { ... },
        func(items []*sdk.Tool) *sdk.ListToolsResult { ... },
    )
}

Future list operations (e.g., listResourceTemplates) become trivial additions.

Verification

make agent-finished passes — all unit and integration tests green.

Fixes #3155
Fixes #3156

[Copilot]

Pull request overview

Refactors the MCP connection’s list* operations to remove duplicated session-check/log/pagination/marshal boilerplate by introducing a reusable generic helper in internal/mcp/connection.go.

Changes:

• Added a generic listMCPItems[Item, Result] helper to centralize common list-operation logic.
• Updated listTools, listResources, and listPrompts to delegate to the helper with type-specific SDK calls/result wrappers.

Show a summary per file

File	Description
internal/mcp/connection.go	Introduces listMCPItems and rewires the three list methods to use it, reducing duplication.

Copilot's findings

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

[Copilot]

The new request log prefix changed from the prior method-style prefixes (e.g., listTools:) to list tools:. If logs are grepped/alerted on by operation name, this change can be disruptive; consider keeping the previous prefix format (e.g., list%s: or passing an explicit operation name like listTools separate from kind).