build: update to Go 1.26

[tembleking]

• Add the new go fix tool to automatically modernize code to newer versions.
• Update dependencies.
• Update base images.
• Build with the newer 1.26 toolchain.

[Copilot]

Pull request overview

This pull request updates the project from Go 1.24 to Go 1.26, leveraging new language features and updating dependencies. The update introduces support for the new go fix tool and adopts Go 1.26's enhanced new() syntax that appears to accept value expressions directly, eliminating the need for custom pointer helper functions.

Changes:

• Upgraded Go toolchain from 1.24 to 1.26 across build configurations
• Replaced custom toPtr/asPtr helper functions with Go 1.26's new(value) syntax throughout the codebase
• Added go fix command integration to the build pipeline and pre-commit hooks
• Updated dependencies (mcp-go, ginkgo, gomega, golang.org/x packages) and base Docker images

Reviewed changes

Copilot reviewed 22 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
package.nix	Updated to use buildGo126Module and refreshed vendorHash for new dependencies
go.mod	Updated Go version to 1.26.0 and bumped dependency versions
go.sum	Updated checksums for new dependency versions
flake.nix	Updated to use go_1_26 in dev environment and removed old go override
flake.lock	Updated nixpkgs to newer revision
justfile	Added fix command using go fix ./... and integrated it into check pipeline
.pre-commit-config.yaml	Added pre-commit hook for go fix
.golangci.yml	Created linter config disabling SA4006/SA4017 for Go 1.26 new() syntax compatibility
docker-base-*.nix	Updated base image digests and hashes
internal/infra/mcp/tools/utils.go	Removed custom toPtr helper function
internal/infra/mcp/tools/tool_list_runtime_events.go	Migrated from toPtr() to new() syntax
internal/infra/mcp/tools/*_test.go	Migrated from toPtr()/asPtr() to new() syntax in test files

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[alecron]

LGTM