ci: unify PR triage and add area labeler

[mulhamna]

Summary

• Replace the standalone pr-triage.yml caller with a unified suiflex.yml workflow, matching the pattern used in other suiflex repositories (e.g. rdb).
• Add a repository-owned path-to-area map so pull requests are labeled automatically by the workspace area they touch.

Changes

• .github/workflows/suiflex.yml (replaces .github/workflows/pr-triage.yml):
  • triage job: unchanged thin caller into suiflex/.github/.github/workflows/pr-triage.yml@main.
  • label job: actions/labeler@v5 with sync-labels: true, using the same suiflex-bot app token so both jobs label as one identity.
• .github/labeler.yml (new): path mapping for area: cli, area: core, area: skills, area: packaging, area: tests, area: ci, area: docs.
• Labels created in the repository before merging so the labeler can apply them.

Test plan

• YAML syntax validated locally (ruby -ryaml) for both files.
• After merge, open or update a PR touching e.g. crates/forgeguard-cli/** and confirm the matching area: cli label is applied by suiflex-bot.
• Confirm a force-push that removes changes from an area drops the corresponding label again (sync-labels).