feat(hooks): use ZENABLE_NONINTERACTIVE for non-interactive installs

[JonZeolla]

Summary

• Replace ZENABLE_YES env var with ZENABLE_NONINTERACTIVE for clarity — the intent is "don't prompt," not "answer yes to everything"
• Simplify post-gen hook: the installer scripts now handle integrations in non-interactive mode, so remove the post-install PATH manipulation and second binary lookup
• When zenable is already installed (skipping the installer), pass -y to zenable install

Companion PR

• Zenable-io/next-gen-governance#5149 — updates install.sh and install.ps1 to support ZENABLE_NONINTERACTIVE and run zenable install -y in non-interactive mode

Test plan

• Verify template generation works with ZENABLE_NONINTERACTIVE=1 set
• Verify template generation works when zenable CLI is already installed (should call zenable install -y)
• Verify template generation works when zenable CLI is not installed (installer handles full flow)
• CI tests pass

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