Gemini CLI v0.61.0

Core Security Hardening: Prevented indirect prompt injection vulnerabilities via build file modifications and untrusted flags, while hardening filesystem boundaries and isolating runtime state ( #29250 by @villahernandez-coder, #29214 by @diegogodinezr).

Agent Loop and Model Stability: Ensured AgentLoopContext state preservation across spread operations and preserved explicit versioned Flash model IDs ( #29335 by @diegogodinezr, #29252 by @SandyTao520).