fix: exempt $MEMORY_DIR/system/ files from read-before-edit gate (#1335)

Co-authored-by: letta-code <248085862+letta-code@users.noreply.github.com>
Co-authored-by: Charles Packer <cpacker@users.noreply.github.com>

src/tools/descriptions/Edit.md

@@ -3,7 +3,7 @@
 Performs exact string replacements in files. 
 
 Usage:
-- You must use your `Read` tool at least once in the conversation before editing. This tool will error if you attempt an edit without reading the file. 
+- You must use your `Read` tool at least once in the conversation before editing. This tool will error if you attempt an edit without reading the file. Exception: files under `$MEMORY_DIR/system/` do not require a Read call first, since their contents are already provided in your system prompt.
 - When editing text from Read tool output, ensure you preserve the exact indentation (tabs/spaces) as it appears AFTER the line number prefix. The line number prefix format is: spaces + line number + tab. Everything after that tab is the actual file content to match. Never include any part of the line number prefix in the old_string or new_string.
 - ALWAYS prefer editing existing files in the codebase. NEVER write new files unless explicitly required.
 - Only use emojis if the user explicitly requests it. Avoid adding emojis to files unless asked.

src/tools/descriptions/Write.md

@@ -4,7 +4,7 @@ Writes a file to the local filesystem.
 
 Usage:
 - This tool will overwrite the existing file if there is one at the provided path.
-- If this is an existing file, you MUST use the Read tool first to read the file's contents. This tool will fail if you did not read the file first.
+- If this is an existing file, you MUST use the Read tool first to read the file's contents. This tool will fail if you did not read the file first. Exception: files under `$MEMORY_DIR/system/` do not require a Read call first, since their contents are already provided in your system prompt.
 - ALWAYS prefer editing existing files in the codebase. NEVER write new files unless explicitly required.
 - NEVER proactively create documentation files (*.md) or README files. Only create documentation files if explicitly requested by the User.
 - Only use emojis if the user explicitly requests it. Avoid writing emojis to files unless asked.