Harden Cobra command behavior: graceful proxy shutdown, default consistency, and completion updates

[Copilot]

This issue identified several Cobra integration gaps in awmg: proxy shutdown was abrupt, proxy --guards-mode used a divergent default, Bash completion was on the legacy generator, and CLI completion/verbosity behavior had minor UX inconsistencies. This PR aligns proxy/root command behavior and modernizes completion wiring with minimal surface-area changes.

• Proxy shutdown semantics

  • proxy now performs graceful HTTP drain on exit (Shutdown + timeout) instead of immediate connection teardown (Close).
  • Shutdown errors are now propagated/logged instead of being silently ignored.
  • Added a named shutdown timeout constant for maintainability.

• guards-mode default alignment

  • proxy --guards-mode now uses difc.DefaultEnforcementMode() instead of a hardcoded literal, matching root command behavior and env-driven defaults.

• Shell completion modernization

  • Switched Bash completion generation to GenBashCompletionV2(..., true) to include richer completion metadata.
  • Replaced manual file-extension completion callbacks for --config and --env with MarkFlagFilename(...) and explicit error handling.

• Verbosity UX cleanup

  • Removed the -v (level 1) informational startup log line that added noise without changing runtime logging behavior.

• Targeted test adjustments

  • Updated/added tests to validate env-driven guards-mode default behavior.
  • Updated completion tests to assert MarkFlagFilename annotations for config/env.
  • Added coverage ensuring -v does not emit extra startup noise.

cmd.Flags().StringVar(&proxyDIFCMode, "guards-mode", difc.DefaultEnforcementMode(), "DIFC enforcement mode: strict, filter, propagate")

const proxyShutdownTimeout = 5 * time.Second
shutdownCtx, cancel := context.WithTimeout(context.Background(), proxyShutdownTimeout)
defer cancel()
if err := httpServer.Shutdown(shutdownCtx); err != nil {
    logger.LogError("shutdown", "HTTP server shutdown error: %v", err)
    return err
}

[Copilot]

Pull request overview

This PR hardens the awmg Cobra CLI by making proxy shutdown behavior graceful, aligning proxy --guards-mode defaults with the root command/environment-driven behavior, and modernizing shell completion generation and flag filename completion metadata.

Changes:

• Implement graceful HTTP server shutdown for awmg proxy using http.Server.Shutdown with a bounded timeout and error propagation.
• Align proxy --guards-mode default to difc.DefaultEnforcementMode() and extend tests to cover env-driven defaults.
• Modernize Bash completion generation (GenBashCompletionV2) and replace manual file-extension completion callbacks with MarkFlagFilename + updated completion tests.

Show a summary per file

File	Description
internal/cmd/root.go	Removes -v info-level startup log noise while keeping higher verbosity/debug logging behavior.
internal/cmd/root_test.go	Adds a regression test asserting -v doesn’t emit startup log output.
internal/cmd/proxy.go	Adds graceful proxy HTTP drain on shutdown and aligns --guards-mode default with difc.DefaultEnforcementMode().
internal/cmd/proxy_test.go	Updates defaults test and adds env-driven default coverage for --guards-mode.
internal/cmd/flags.go	Switches config/env completions to MarkFlagFilename(...) with error handling.
internal/cmd/flags_test.go	Updates tests to assert Cobra filename-extension annotations instead of custom completion funcs.
internal/cmd/completion.go	Switches Bash completion generation to GenBashCompletionV2(..., true) for richer metadata.

Copilot's findings

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• Files reviewed: 7/7 changed files
• Comments generated: 0