Greptile Summary

This PR adds log.warn() calls at the two code paths in agentCommandInternal where a session model override can be silently dropped because the model is not in the runtime allowlist — fixing a diagnosability gap where sessions_spawn callers would see modelApplied: true but the agent would run on the default model with no indication of why.

• Block 1 (src/commands/agent.ts ~line 704): Warning is emitted before the stored override is cleared from the session entry and persisted to disk, giving the caller a clear signal that the stored override was invalid at runtime.
• Block 2 (src/commands/agent.ts ~line 740): Warning is emitted in the new else branch for the case where the provider/model variables are not updated (e.g. when sessionStore or sessionKey is absent), so callers always see a warning regardless of whether the entry can be persisted.
• No double-warning scenario exists: applyModelOverrideToSessionEntry(isDefault: true) deletes entry.modelOverride, ensuring Block 2's if (storedModelOverride) guard short-circuits when Block 1 has already run.
• Both warning messages are actionable, naming the blocked model and pointing to the models.allowed / models.allowAny config keys.

Confidence Score: 5/5

• Safe to merge — the change is purely additive (two log.warn calls) with no modifications to existing logic or state.
• The diff is minimal and touches only two logging sites. The warning placement in both blocks is logically correct, the messages are actionable, and a double-warning race is provably impossible because applyModelOverrideToSessionEntry(isDefault: true) deletes modelOverride, causing Block 2's guard to short-circuit. No behavioural change was made to the actual model-selection logic.
• No files require special attention.

_{Last reviewed commit: 5cd5e43}