gopls/internal/mcp: avoid pointless diagnostics in the edit workflow

In practice, I frequently see models make a plan that involves multiple
files, edit just one of those files, and then run diagnostics, only to
observe that diagnostics in related files are consistent with the plan.

Hint to apply all edits before running diagnostics, to avoid churn.

Change-Id: I16183b3b05638cbf5a1be1a92759e144aca896cc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/687876
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Hongxiang Jiang <[email protected]>
Auto-Submit: Robert Findley <[email protected]>

Author: findleyr

gopls/internal/mcp/instructions.md

@@ -36,7 +36,7 @@ The editing workflow is iterative. You should cycle through these steps until th
 2. **Find references**: Before modifying the definition of any symbol, use the `go_symbol_references` tool to find all references to that identifier. This is critical for understanding the impact of your change. Read the files containing references to evaluate if any further edits are required.
    EXAMPLE: `go_symbol_references({"file":"/path/to/server.go","symbol":"Server.Run"})`
 
-3. **Make edits**: Make the primary edit, as well as any edits to references you identified in the previous step.
+3. **Make edits**: Make the required edits, including edits to references you identified in the previous step. Don't proceed to the next step until all planned edits are complete.
 
 4. **Check for errors**: After every code modification, you MUST call the `go_diagnostics` tool. Pass the paths of the files you have edited. This tool will report any build or analysis errors.
    EXAMPLE: `go_diagnostics({"files":["/path/to/server.go"]})`