fix(security): validate script templates before base64 encoding

[la14-1]

Why: Prevents future regression where template variable interpolation before base64 encoding could allow command injection in systemd services running with root privileges on remote VMs.

Fixes #3130

Changes

• Add pre-encoding validation in startGateway() (agent-setup.ts)
• Add pre-encoding validation in setupAutoUpdate() (agent-setup.ts)
• Add pre-encoding validation in injectSpawnSkill() (spawn-skill.ts)

The validation checks that script templates don't contain ${ interpolation patterns before base64 encoding, as defense-in-depth against future changes that might add template variable interpolation.

-- refactor/security-auditor

[louisgv]

Security Review

Verdict: APPROVED ✅

Commit: 7a257c3

Summary

This PR adds defense-in-depth validation to prevent accidental JS template literal interpolation in script templates before base64 encoding. The implementation is sound and improves security posture.

Changes Reviewed

• packages/cli/src/shared/agent-setup.ts: Added validateScriptTemplate() function and applied it to gateway/auto-update systemd units
• packages/cli/src/shared/spawn-skill.ts: Applied validation to spawn skill content
• packages/cli/package.json: Version bump 0.30.1 → 0.30.2

Security Findings

None — No security issues identified.

Positive Security Aspects

• ✅ Prevents template literal interpolation before encoding (defense-in-depth)
• ✅ Regex pattern /\$\{/ is precise and appropriate
• ✅ Error messages are clear without leaking sensitive data
• ✅ Validation placement is correct (before encoding)
• ✅ Existing base64 validation remains intact
• ✅ No command injection vectors
• ✅ No credential exposure risks
• ✅ Proper ESM conventions

Tests

• TypeScript tests: ✅ PASS (2023/2023 tests passed)
• Shell scripts: N/A (no .sh files modified)

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-- security/pr-reviewer