Fixes #5294: Add instruction to Architect mode to avoid time estimates

- Updated Architect mode custom instructions to explicitly prohibit providing time estimates
- Added clear guidance to focus on actionable plans without speculating about implementation timeframes
- Updated test snapshot to reflect the new instruction
- All tests passing

Author: roomote

src/core/prompts/__tests__/__snapshots__/add-custom-instructions/architect-mode-prompt.snap

@@ -487,6 +487,8 @@ Mode-specific Instructions:
 
 6. Use the switch_mode tool to request that the user switch to another mode to implement the solution.
 
+**IMPORTANT: Do not provide time estimates for how long tasks will take to complete. Focus on creating clear, actionable plans without speculating about implementation timeframes.**
+
 Rules:
 # Rules from .clinerules-architect:
 Mock mode-specific rules

src/shared/modes.ts

@@ -72,7 +72,7 @@ export const modes: readonly ModeConfig[] = [
 		description: "Plan and design before implementation",
 		groups: ["read", ["edit", { fileRegex: "\\.md$", description: "Markdown files only" }], "browser", "mcp"],
 		customInstructions:
-			"1. Do some information gathering (for example using read_file or search_files) to get more context about the task.\n\n2. You should also ask the user clarifying questions to get a better understanding of the task.\n\n3. Once you've gained more context about the user's request, you should create a detailed plan for how to accomplish the task. Include Mermaid diagrams if they help make your plan clearer.\n\n4. Ask the user if they are pleased with this plan, or if they would like to make any changes. Think of this as a brainstorming session where you can discuss the task and plan the best way to accomplish it.\n\n5. Once the user confirms the plan, ask them if they'd like you to write it to a markdown file.\n\n6. Use the switch_mode tool to request that the user switch to another mode to implement the solution.",
+			"1. Do some information gathering (for example using read_file or search_files) to get more context about the task.\n\n2. You should also ask the user clarifying questions to get a better understanding of the task.\n\n3. Once you've gained more context about the user's request, you should create a detailed plan for how to accomplish the task. Include Mermaid diagrams if they help make your plan clearer.\n\n4. Ask the user if they are pleased with this plan, or if they would like to make any changes. Think of this as a brainstorming session where you can discuss the task and plan the best way to accomplish it.\n\n5. Once the user confirms the plan, ask them if they'd like you to write it to a markdown file.\n\n6. Use the switch_mode tool to request that the user switch to another mode to implement the solution.\n\n**IMPORTANT: Do not provide time estimates for how long tasks will take to complete. Focus on creating clear, actionable plans without speculating about implementation timeframes.**",
 	},
 	{
 		slug: "code",