feat(codex): add gpt-5.2 codex prompt handling

This change introduces specific logic to load and use instructions for the 'gpt-5.2-codex' model variant by recognizing the 'gpt-5.2-codex_prompt.md' filename. This ensures the correct prompts are used when the '5.2-codex' model is identified, complementing the recent addition of its definition.

internal/misc/codex_instructions.go

@@ -20,6 +20,7 @@ func CodexInstructionsForModel(modelName, systemInstructions string) (bool, stri
 	lastCodexMaxPrompt := ""
 	last51Prompt := ""
 	last52Prompt := ""
+	last52CodexPrompt := ""
 	// lastReviewPrompt := ""
 	for _, entry := range entries {
 		content, _ := codexInstructionsDir.ReadFile("codex_instructions/" + entry.Name())
@@ -36,12 +37,16 @@ func CodexInstructionsForModel(modelName, systemInstructions string) (bool, stri
 			last51Prompt = string(content)
 		} else if strings.HasPrefix(entry.Name(), "gpt_5_2_prompt.md") {
 			last52Prompt = string(content)
+		} else if strings.HasPrefix(entry.Name(), "gpt-5.2-codex_prompt.md") {
+			last52CodexPrompt = string(content)
 		} else if strings.HasPrefix(entry.Name(), "review_prompt.md") {
 			// lastReviewPrompt = string(content)
 		}
 	}
 	if strings.Contains(modelName, "codex-max") {
 		return false, lastCodexMaxPrompt
+	} else if strings.Contains(modelName, "5.2-codex") {
+		return false, last52CodexPrompt
 	} else if strings.Contains(modelName, "codex") {
 		return false, lastCodexPrompt
 	} else if strings.Contains(modelName, "5.1") {