Fix conflicting instructions about backticks vs markdown links for file references

[Copilot]

GPT-5 mini was wasting thinking budget on conflicting instructions: fileLinkificationInstructions forbade backticks for files, while multiple prompt files instructed wrapping "filename or symbol" in backticks.

Changes

Clarified the distinction across all agent prompts:

• Symbols (classes, methods, variables, constants) → backticks: MyClass, handleClick()
• Filenames and paths → markdown links: [src/file.ts](src/file.ts)

Updated instructions in:

• fileLinkificationInstructions.tsx - Added explicit note that backticks are ONLY for symbols, NOT files
• defaultAgentInstructions.tsx - Split "filename or symbol" into two separate rules with updated examples
• gpt5Prompt.tsx, gpt51Prompt.tsx, gpt5CodexPrompt.tsx, hiddenModelBPrompt.tsx - Clarified symbol vs filename formatting

Before:

When referring to a filename or symbol in the user's workspace, wrap it in backticks.
<example>
  The class `Person` is in `src/models/person.ts`.
</example>

After:

When referring to symbols (classes, methods, variables, constants) in the user's workspace, wrap them in backticks. 
For filenames and paths, use markdown links as specified in the fileLinkification section.
<example>
  The class `Person` is in [src/models/person.ts](src/models/person.ts).
</example>

Test snapshots updated to reflect the instruction changes.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• update.code.visualstudio.com
  • Triggering command: /opt/hostedtoolcache/node/22.21.1/x64/bin/node node /home/REDACTED/work/vscode-copilot-chat/vscode-copilot-chat/node_modules/.bin/vscode-test (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>GPT-5 mini complains system instructions on links are conflicting, and they are actually conflicting</issue_title>
<issue_description>Version: 1.108.0-insider (Universal)
Commit: 9ba40f8204f1b4cb092f9585b19ab3f26d0a588c
Date: 2025-12-12T14:19:49.836Z
Electron: 39.2.3
ElectronBuildId: 12895514
Chromium: 142.0.7444.175
Node.js: 22.21.1
V8: 14.2.231.21-electron.0
OS: Darwin arm64 24.6.0

Name: GitHub Copilot Chat
Id: GitHub.copilot-chat
Description: AI chat features powered by Copilot
Version: 0.36.2025121203
Publisher: GitHub
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=GitHub.copilot-chat

This is a waste of the thinking budget.

GPT-5 mini complains in the thinking output:

I’m stuck navigating conflicting instructions about using backticks for filenames. On one hand, I'm told to wrap filenames in backticks in the user's workspace, but then there's a strict rule against backticks in file paths. To be cautious, I’ll avoid backticks altogether when referencing the file.

They are right:

- Wrap symbol names (classes, methods, variables) in backticks: `MyClass`, `handleClick()`
- When mentioning files or line numbers, always follow the rules in fileLinkification section below:<fileLinkification>
When mentioning files or line numbers, always convert them to markdown links using workspace-relative paths and 1-based line numbers.
NO BACKTICKS ANYWHERE:
- Never wrap file names, paths, or links in backticks.
- Never use inline-code formatting for any file reference.

REQUIRED FORMATS:
- File: [path/file.ts](path/file.ts)
- Line: [file.ts](file.ts#L10)
- Range: [file.ts](file.ts#L10-L12)

<importantReminders>
...
When referring to a filename or symbol in the user's workspace, wrap it in backticks.

</importantReminders>

</issue_description>

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

• Fixes GPT-5 mini complains system instructions on links are conflicting, and they are actually conflicting vscode#283488

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