Actualize nelm engine: extract NelmEngine with DI, add helm-render rule

[diyliv]

Summary

Refactor the monolithic internal/helm/render.go into a pluggable NelmEngine following the d8-package-plugin architecture, and add a configurable helm-render rule to the templates linter.

Changes

Action	File	Purpose
Create	internal/helm/engine.go	NelmEngine with DI via EngineOption functional options
Modify	internal/helm/render.go	Renderer delegates to NelmEngine internally
Modify	pkg/config.go	HelmRenderRule in TemplatesLinterRules
Modify	pkg/config/linters_settings.go	mapstructure type helm-render
Modify	pkg/config/global/global.go	global config field
Modify	internal/module/module.go	values field + GetValues() + config wiring
Create	internal/module/helm_overrides.go	Export HelmLibOverrides() for shared use
Create	pkg/linters/templates/rules/helm_render.go	HelmRenderRule with Check()
Create	pkg/linters/templates/rules/helm_render_test.go	Unit tests
Modify	pkg/linters/templates/templates.go	Register helm-render rule in linter

Architecture

Before:  Renderer (monolith) -> nelm chart loader/engine
After:   NelmEngine (DI) -> loaded by Rules -> through Linters -> managed by Manager
                              ^
         HelmRenderRule ------+ (pluggable, configurable via .dmt.yaml)

Config

# .dmt.yaml
linters-settings:
  templates:
    rules:
      helm-render: warn  # per-rule severity

Verification

• All existing tests pass (internal/helm: 3/3, module, templates rules)
• New helm_render_test.go passes
• go vet clean on all affected packages
• Full go test ./internal/... ./pkg/... passes