Add tree-sitter HCL/Terraform grammar support for .tf files

[connelldave]

Summary

The code tool's tree-sitter-based operations (get_document_symbols, search_symbols, lookup_symbols, pattern_search, pattern_rewrite) don't support Terraform/HCL (.tf, .tfvars) files.

Steps to Reproduce

1. Open a workspace containing .tf files
2. Ask the assistant to get document symbols from a .tf file
3. The code tool returns: "Failed to get document symbols: Unsupported file extension: tf"

Expected Behavior

Tree-sitter operations should work with .tf files. A tree-sitter HCL grammar already exists: https://github.com/tree-sitter-grammars/tree-sitter-hcl

Current Behavior

The built-in tree-sitter support is limited to 18 languages with no way to add custom grammars. The only extensibility point is custom LSP servers via lsp.json, which covers LSP operations but not tree-sitter-based ones (symbol search, pattern matching, etc.).

Suggestion

Either:

1. Bundle tree-sitter-hcl as a 19th built-in grammar, or
2. Provide a plugin mechanism to load custom tree-sitter grammars (similar to how lsp.json allows custom language servers)

[github-actions]

🤖 Potential Duplicate Detected

This issue appears to be similar to:

• #6040: Add Apex Language Support to Code Intelligence (85% similar)

What happens next?

• ⏰ This issue will be automatically closed in 3 days
• 🏷️ If this is not a duplicate, you can prevent automatic closure by adding a comment or reacting with 👎 to this message.
• 💬 Comment on the original issue if you have additional information

Why is this marked as duplicate?
Both issues request adding support for new programming languages to code intelligence features - new issue wants HCL/Terraform support while #6040 wants Apex support. Same core feature request pattern for extending language support in tree-sitter operations.

[connelldave]

is that bot useful normally? Not a duplicate

[github-actions]

Thank you for your feedback! 🙏

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