VSCode dev config: exclude .builders/ + node_modules from watch/search; drop Extension Test Runner recommendation

[amrmelsayed]

Problem

Opening the repo in VSCode and accepting the recommended extensions installs ms-vscode.extension-test-runner (listed in .vscode/extensions.json). On a workspace that contains agent-farm builder worktrees (.builders/*/), that extension's test discovery runs:

rg --files --hidden --no-require-git --no-ignore --follow -g <wt>/node_modules/.pnpm/node_modules/codev-vscode/out/test/**/*.test.js

Because --no-ignore skips .gitignore (so node_modules/.builders aren't excluded) and --follow chases symlinks, it walks every builder worktree's pnpm symlink farm. With ~15 worktrees this spawns a flood of rg processes and pegs CPU for ~30s at a time, recurring on file changes.

The cost is entirely in the rg walks — an extension-host CPU profile captured during the storm was ~99% idle, so no extension code is the consumer.

Root cause (both pieces are repo-provided)

1. .vscode/extensions.json recommends the test-runner extension.
2. .vscode/settings.json has no files.watcherExclude / search.exclude for .builders/ or node_modules, so VSCode (and any tool it drives) traverses the worktree farm.

The repo both creates the .builders/* worktree farm and recommends an extension that walks it — they collide.

Proposed fix

• Add to .vscode/settings.json:

  "files.watcherExclude": { "**/.builders/**": true, "**/node_modules/**": true },
  "search.exclude":       { "**/.builders/**": true, "**/node_modules/**": true }

• Remove ms-vscode.extension-test-runner from .vscode/extensions.json recommendations (keep dbaeumer.vscode-eslint and connor4312.esbuild-problem-matchers, which remain useful for the vscode package). Do not delete the file.
• Optionally update packages/vscode/vsc-extension-quickstart.md, which also references the test-runner extension.

Notes

• The excludes are worth having as defense-in-depth even with the recommendation removed — any tool that walks the tree (search, quick-open, other extensions) benefits.
• Incidentally discovered while reviewing the codelens work (vscode: inject file/hunk reference into builder PTY from the unified-diff editor (codelens) #789); unrelated to that feature.

[amrmelsayed]

On it! Working on a fix now.