Refactor duplicated helper logic for session logging, rate-limit parsing, and routed server setup

[Copilot]

This change addresses several small but recurring organization issues surfaced by the semantic clustering analysis: duplicated session-ID logging logic, split GitHub rate-limit parsing, a trivial logger alias, a misplaced tool-classification helper, and HTTP server factory functions split across files. The intent is to reduce duplication and make these helpers easier to find and evolve without changing behavior.

• Session ID log formatting

  • Added util.FormatSessionIDForLog as the shared log-safe session ID formatter.
  • Updated server and launcher logging paths to use the same truncation behavior, so launcher logs no longer emit full session IDs while server logs keep existing semantics.

• GitHub rate-limit parsing

  • Moved reset-time parsing into internal/githubhttp/rate_limit.go.
  • Kept both parsing concerns together:
    • ParseRateLimitResetHeader for X-RateLimit-Reset
    • ParseRateLimitResetFromText for MCP/tool error text such as rate reset in 42s
  • Updated server-side circuit-breaker logic and tests to consume the shared parser.

• Helper placement and indirection cleanup

  • Removed the trivial truncateSanitized wrapper and used util.Truncate directly at call sites.
  • Moved IsSingularReadTool from internal/difc to internal/mcp, which better matches its role as a tool-naming heuristic rather than DIFC logic.
  • Relocated CreateHTTPServerForRoutedMode into internal/server/http_server.go so HTTP server factory functions live together.

• Targeted test updates

  • Moved and preserved edge-case coverage for IsSingularReadTool under internal/mcp.
  • Updated session logging and rate-limit parsing tests to follow the shared helpers and preserve previous behavioral coverage.

Example of the new shared session-ID formatting path:

func FormatSessionIDForLog(sessionID string) string {
	const sessionIDLogMaxLen = 8
	if sessionID == "" {
		return "(none)"
	}
	return Truncate(sessionID, sessionIDLogMaxLen)
}