Accept common XML tool name aliases (fixes #967)

[bouclem]

What

Fixes #967.

When a model outputs an XML tool call using a hallucinated tag like
<write_file> with <path> / <content>, the IDE rendered it as
plain text instead of executing the tool. The XML parser in
extractGrammar.ts only recognized exact canonical tool/param tags
from availableTools(), so any drift went straight through as raw
output.

This adds a small alias table so a few well-known wrong names get
mapped back to the real tools, with canonical param keys, before the
result is handed off to the rest of the pipeline. Compliant models
are unaffected.

Aliases added

• write_file -> rewrite_file (path -> uri, content -> new_content)
• create_file -> create_file_or_folder (path -> uri)
• delete_file -> delete_file_or_folder (path -> uri)

Param aliases are scoped per tool to avoid cross-tool collisions.

Also

One line added to the XML tool-calling guidelines in
prompts.ts asking the model to use the exact tool and parameter
names listed and not invent new tags. Cheap nudge for compliant
models, doesn't replace the alias map.

Notes

• No public API changes.
• Aliases only kick in when a tag is otherwise unrecognized, so
  there's no behavior change for models that follow the prompt.
• Easy to extend later if more common wrong names show up.

Test

Reproduced the failure mode from #967 by piping an LLM-style stream
that contains <write_file><path>...</path><content>...</content></write_file>.
With the change, the parser emits a rewrite_file tool call with
uri and new_content populated. Without the change, the same
stream renders as plain text, matching the bug report.