chore: add update-packages skill for Copilot CLI

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: chrisjwalk-bot

.github/skills/update-packages/SKILL.md

@@ -0,0 +1,104 @@
+---
+name: update-packages
+description: >
+  Update all npm packages to their latest versions using the update-packages
+  script. Use this when asked to update, upgrade, or consolidate dependencies,
+  or to close dependabot PRs.
+---
+
+## Update Packages Workflow
+
+Follow these steps in order.
+
+### 1. Create a GitHub issue (as `chrisjwalk`)
+
+```bash
+gh issue create --title "chore: update all packages to latest" --body "..."
+```
+
+Note the issue number (e.g. #42).
+
+### 2. Create a branch off main
+
+```bash
+git checkout main && git pull
+git checkout -b feat/consolidate-deps-<issue-number>
+```
+
+### 3. Run the update-packages script
+
+Always omit `typescript` — upgrading TypeScript is a breaking change that
+requires a dedicated branch and tsconfig work (see issue #101 for context).
+
+```bash
+npx ts-node ./tools/update-packages/src/main.ts --omit typescript --interactive false
+```
+
+The script will:
+
+- Detect all outdated packages via `pnpm outdated`
+- Run `nx migrate <pkg>@latest` for each one
+- Merge any generated migrations into `migrations.json`
+- Print next steps (install + run migrations if needed)
+
+### 4. Install updated packages
+
+```bash
+pnpm install --no-frozen-lockfile
+```
+
+If the install fails, check for postinstall build errors (e.g. tsconfig
+issues in `tools/builders/dotnet-builder`).
+
+### 5. Run migrations (only if migrations.json was updated)
+
+```bash
+npx nx migrate --run-migrations
+```
+
+### 6. Run all tests
+
+```bash
+nx reset
+nx run-many -t build,test
+```
+
+All 9 projects must pass before committing.
+
+### 7. Commit
+
+```bash
+git add -A
+git commit -m "chore: update all packages to latest (closes #<issue-number>)
+
+Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>"
+```
+
+### 8. Push and open PR as `chrisjwalk-bot`, then switch back
+
+```bash
+gh auth switch --user chrisjwalk-bot
+git push origin feat/consolidate-deps-<issue-number>
+gh pr create --title "chore: update all packages to latest" --body "Closes #<issue-number> ..."
+gh auth switch --user chrisjwalk
+```
+
+### 9. Close stale dependabot PRs
+
+Close any open dependabot PRs that are now covered by this update:
+
+```bash
+gh pr list --author "app/dependabot" --json number,title
+gh pr close <number> --comment "Covered by consolidated update PR" --delete-branch
+```
+
+Leave open any dependabot PRs for packages that were intentionally omitted
+(e.g. TypeScript major version bumps).
+
+## Notes
+
+- `typescript` is always omitted — track TS upgrades separately in issue #101
+- If a package is a transitive dep not shown by `pnpm outdated`, use
+  `pnpm.overrides` in `package.json` to force the version
+- After merging, watch for new dependabot PRs — dependabot may recreate stale
+  ones; close them if the package was already updated