docs(checklist): switch tmp/.terraform exclusions to .git/info/exclude

- Replace the "add tmp/ to .gitignore" guidance with a stronger
  policy: put **/tmp/, .terraform/, and .terragrunt-cache/ in
  .git/info/exclude instead of the committed .gitignore. These
  are personal / per-clone workspaces and tool caches, not
  project-wide policy; .git/info/exclude keeps them out of your
  working tree without imposing the convention on every collaborator
- Include the heredoc one-liner to append all three patterns at once
- Include a rationale paragraph so future readers understand why this
  policy exists (the choice is intentional, not an oversight)
- Bundle a pre-existing local edit that expands the workspace tmp/
  scaffold from a single tmp/ to four subdirectories used by other
  workflows: tmp/pr, tmp/pr_reviews, tmp/agent_reports, tmp/bug_reports

Fixes the smart-quote (U+2019) in the old line as a side effect of
the replacement, keeping the file consistent with the repo's
plain-ASCII punctuation convention (commit 3761314).

Author: d-padmanabhan

NEW_REPO_CHECKLIST.md

@@ -28,7 +28,7 @@ readlink .cursor/rules
 - [ ] Create `tmp/tasks.md` (minimum)
 
 ```bash
-mkdir -p tmp
+mkdir -p tmp/pr tmp/pr_reviews tmp/agent_reports tmp/bug_reports
 cp .cursor/rules/templates/tasks.md.template tmp/tasks.md
 ```
 
@@ -46,9 +46,14 @@ cp .cursor/rules/templates/progress.md.template tmp/progress.md
 
 ## Git hygiene (recommended)
 
-- [ ] Ensure `tmp/` is ignored (add to your repo’s `.gitignore`):
+- [ ] **Git Hygiene:** Add the following to `.git/info/exclude` (preferred) instead of the repo `.gitignore`: `**/tmp/`, `.terraform/`, `.terragrunt-cache/`. Do not modify the repo `.gitignore` for these entries.
 
-```gitignore
-# Private/local documentation
-tmp/
+```bash
+cat >> .git/info/exclude <<'EOF'
+**/tmp/
+.terraform/
+.terragrunt-cache/
+EOF
 ```
+
+Rationale: these are personal / per-clone workspaces and tool caches, not project-wide policy. `.git/info/exclude` keeps them out of *your* working tree without imposing the convention on every collaborator via the committed `.gitignore`.