Add Developer Experience docs: debugging, startup performance, and hot reload

[Copilot]

• Create fundamentals/debug-aspire-apps.mdx - Debugging guide covering VS Code, Visual Studio, Rider, and other IDEs; selective debugging; Linux debugging
• Create fundamentals/startup-performance.mdx - Performance/startup optimization guide covering NuGet restore, container pull, and app host startup
• Create fundamentals/hot-reload.mdx - Watch mode/hot reload guide covering current status, limitations, and workarounds
• Update docs.topics.ts sidebar to include the new pages under Fundamentals
• Replace <kbd> with <Kbd> component (from starlight-kbd/components) in debug-aspire-apps.mdx
• Run doc-tester validation — found and fixed two issues:
  • Removed aspire run --no-dashboard (non-existent CLI flag) from startup-performance.mdx
  • Removed misleading WithEnvironment("DOTNET_WATCH", "1") code example from hot-reload.mdx

Original prompt

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This section details on the original issue you should resolve

<issue_title>[GitHub Discussions] Developer Experience & Tooling gaps</issue_title>
<issue_description>## Summary

Based on analysis of 820 GitHub discussions from dotnet/aspire.

Question counts:

Topic	Questions
DevEx/Tooling	60 total
Performance/Slow	15+
Debugging	10+
IDE Issues	10+
CLI	15+

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Critical Gaps

1. ❌ Debugging Guide (CRITICAL)

Discussions:

• Allow running and debugging a Linux-only project on aspire dotnet/aspire#12561: Allow running and debugging a Linux-only project on aspire
• Localized file check-in by OneLocBuild Task: Build definition ID 1309: Build ID 2816277 dotnet/aspire#12039: .Net Aspire Single Service Nvim Debugging
• Is this a bug? dotnet/aspire#9846: Is this a bug?

Customer Questions:

• Debugging specific services
• Selective debugging (debug some, not others)
• Linux-only project debugging
• Non-VS debugging (Neovim, etc.)

Action Items:

• Debugging guide (all IDEs)
• Selective service debugging
• Linux debugging patterns
• Non-VS IDE debugging

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2. ❌ Performance/Slow Startup (15+ questions)

Discussions:

• Why are Aspire projects taking so long to be restored? It's more than 2 mins every single time. dotnet/aspire#12518: Why are Aspire projects taking so long to be restored? It's more than 2 mins every single time
• Optimizing app host start up time dotnet/aspire#13840: Optimizing app host start up time

Customer Questions:

• NuGet restore taking too long
• App host startup optimization
• Container pull slowness

Action Items:

• Performance optimization guide
• NuGet restore troubleshooting
• Startup optimization patterns

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3. ⚠️ IDE-Specific Issues

Discussions:

• Using GH Copilot in Aspire in Rider and other IDEs dotnet/aspire#10168: Using GH Copilot in Aspire in Rider and other IDEs
• Rider, VS Code extension issues mentioned across discussions

Customer Questions:

• Rider integration
• VS Code extension issues
• GitHub Copilot integration

Action Items:

• IDE comparison guide
• Rider-specific documentation
• VS Code troubleshooting

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4. ⚠️ Watch Mode / Hot Reload

No dedicated discussions, but Discord shows high demand (42 questions)

Action Items:

• Watch mode current status
• Hot reload limitations
• Workarounds

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Data Source

• GitHub Discussions: 820 total
• DevEx-related: 60 discussions
• Date range: Project inception - February 2026
  </issue_description>

<agent_instructions>Please address this issue, while using the .github/skills/doc-writer/SKILL.md. Be certain to also take into account, related issues, pull requests, and comments that are directly linked as well as comments.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [GitHub Discussions] Developer Experience & Tooling gaps #351

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[IEvangelist]

This PR looks good so far, but let's double check it for accuracy by using the .github/skills/doc-tester/SKILL.md skill. Please also consider all new comments and feedback. @copilot

[IEvangelist]

Please import the { Kbd } component and use that instead <kbd> throughout this doc.

[Copilot]

Done in cf34df5 — imported { Kbd } from starlight-kbd/components and replaced all three <kbd> instances with <Kbd windows='...' mac='...' /> props.

[Copilot]

This PR looks good so far, but let's double check it for accuracy by using the .github/skills/doc-tester/SKILL.md skill. Please also consider all new comments and feedback. @copilot

Doc-tester validation complete (823379b). Two issues were found and fixed:

1. startup-performance.mdx — Removed the "Disable the dashboard for headless scenarios" subsection which referenced aspire run --no-dashboard, a flag that doesn't exist in aspire run (confirmed against the CLI reference docs).

2. hot-reload.mdx — Removed the misleading WithEnvironment("DOTNET_WATCH", "1") AppHost code example. Setting that env var on a project resource does not invoke dotnet watch or enable hot reload — the correct approach (running dotnet watch run in a separate terminal) is now the sole recommendation in that section.

All internal links, imports, Kbd usage, and other technical claims passed validation.