feat(kiloclaw-customizer): add KiloClaw platform constraint instructions

[alexkgold]

Summary

• Adds a ## KiloClaw Platform section to the system prompt injected by the kiloclaw-customizer plugin
• Instructs the assistant that users have no CLI/SSH access and to offer to act on their behalf instead
• Covers four constraint areas: CLI access, default model changes, upgrades, exec permissions, and supported channels
• Uses bold topic labels and flat imperative paragraphs, with explicit override language to supersede conflicting base prompt guidance (e.g. openclaw status self-run instructions)

Verification

• Reviewed final prompt text in plugins/kiloclaw-customizer/src/index.ts
• N/A for automated tests (prompt-only change)

Visual Changes

N/A

Reviewer Notes

The added text is appended via appendSystemContext at priority: 50, which places it after the cache boundary in the base system prompt under ## Group Chat Context. The CLI override sentence explicitly references the base prompt's openclaw status instruction to ensure precedence is clear to the model.