Refactor DIFC tool classification placement and extract middleware content-rewrite helpers

[Copilot]

Semantic clustering flagged two structural outliers: isSingularReadTool lived in tool registration code despite being DIFC-only, and jqschema.go still contained a cohesive content-rewrite helper block better separated from jq/schema logic. This PR performs those refactors without changing behavior.

• DIFC helper co-location

  • Moved isSingularReadTool(toolName string) bool from internal/server/tool_registry.go to internal/server/difc_log.go.
  • Keeps DIFC response/error shaping helpers (buildDIFCSingleItemFilteredError, notices, logging) in one place and removes DIFC-specific logic from tool registration.

• Middleware rewrite-cluster extraction

  • Created internal/middleware/content_rewrite.go.
  • Moved the envelope/text rewrite helpers out of internal/middleware/jqschema.go:
    • rewriteFilteredTextPayload
    • rewriteEnvelopeTextPayload
    • rewriteFirstContentItem
    • rewriteContentItemText
  • Leaves jqschema.go focused on jq filter compilation/execution and middleware flow.

• Behavior-preserving refactor

  • Function signatures and call sites remain unchanged; only file placement/organization changed.

// now in internal/server/difc_log.go
func isSingularReadTool(toolName string) bool {
	singular := !strings.HasPrefix(toolName, "list_") && !strings.HasPrefix(toolName, "search_")
	logDifcLog.Printf("isSingularReadTool: toolName=%s, singular=%v", toolName, singular)
	return singular
}

[Copilot]

Pull request overview

Refactors DIFC- and middleware-related helpers into more cohesive locations to keep tool registration and jq/schema middleware logic focused, without intended behavior changes.

Changes:

• Moved isSingularReadTool from internal/server/tool_registry.go into internal/server/difc_log.go alongside other DIFC response/error shaping helpers.
• Extracted content-rewrite helpers (rewriteFilteredTextPayload, rewriteEnvelopeTextPayload, rewriteFirstContentItem, rewriteContentItemText) out of internal/middleware/jqschema.go into a new internal/middleware/content_rewrite.go.
• Kept existing signatures and call sites intact to preserve behavior.

Show a summary per file

File	Description
internal/server/tool_registry.go	Removes DIFC-specific helper to keep tool registration focused.
internal/server/difc_log.go	Co-locates DIFC helper (isSingularReadTool) with DIFC logging/error shaping logic.
internal/middleware/jqschema.go	Removes extracted content-rewrite helper block to narrow file focus to jq/schema middleware flow.
internal/middleware/content_rewrite.go	New file containing the extracted content-rewrite helper functions.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

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