ci: skip build, tests and deploy for docs-only changes (main)

[saqibmanan]

A docs-only change (Markdown anywhere, docs/, cds_docs_femhealth/) no longer runs the build check, the full test suite or a deploy.

Workflow	Change
deploy-Dataspace.yml (push dev/main)	paths-ignore: no dev or prod deploy for docs-only pushes
deploy-IDS-Dataspace.yml (push dev)	paths-ignore
pre-merge.yml (push/PR dev)	paths-ignore on both triggers
pr-gate.yml (PR → main)	New changes job lists the PR's files. Full Suite (dev) runs only if any are code. New PR Gate job reports success when the suite passed or was skipped.

Why pr-gate doesn't just use paths-ignore: its checks are required on main. A required check that never reports leaves a docs-only PR stuck at "Expected — waiting" and unmergeable.

Any change with at least one code file runs everything as before. The filter, run against real PRs: #477 → docs-only, #475 → 22 code files, full suite.

After merging into main: switch branch protection (admin)

Replace the three required contexts with the single PR Gate check:

gh api -X PATCH repos/CivicDataLab/DataSpaceFrontend/branches/main/protection/required_status_checks \
  -f 'contexts[]=PR Gate' -F strict=false

Do this only after the main PR merges. Open PRs whose branches predate this change never report PR Gate, so they would be blocked until they're updated from main.