ci: extract changes-filter composite action; fix docs-only PR stall (#11785)

## Summary

Extract a `.github/actions/changes-filter` composite action and adopt it
across path-gated CI workflows, fixing the docs-only PR stall and
removing duplicated `paths:` / `paths-ignore:` filtering across 8
workflows.

## Background

Docs-only PRs stalled on required status checks because workflows using
`paths-ignore: ['**/*.md']` never created a check run, while branch
protection still required it. Observed on #11776 (the `test` check from
`ci-tests-unit.yaml` never appeared).

The fix pattern: keep the workflow triggered, gate downstream jobs on a
`changes` job whose outputs are computed from a path filter. Skipped
jobs count as passing under branch protection.

## What the action emits

| Output | Meaning |
|---|---|
| `should-run` | Any file outside `apps/`, `docs/`, `.storybook/`,
`**/*.md` changed. |
| `app-website-changes` | Shared deps or `apps/website/**` changed. |
| `app-desktop-changes` | Shared deps or `apps/desktop-ui/**` changed. |
| `app-frontend-changes` | Shared deps or `src/**` changed. |
| `packages-changes` | Shared deps or `packages/**` changed. |
| `storybook-changes` | Shared deps or `.storybook/**` changed. |
| `docs-changes` | `docs/**` or any `**/*.md` changed (deps NOT folded
in). |
| `dependency-changes` | Root `package.json`, `pnpm-lock.yaml`, or
`pnpm-workspace.yaml` changed. |

Shared deps are folded into every `app-*`, `packages-changes`, and
`storybook-changes` output so a lockfile bump correctly invalidates each
granular gate. Outputs default to `'true'` for non-`pull_request` events
to avoid the silent-skip footgun on push / merge_group.

## Workflows migrated

| Workflow | Gate | Notes |
|---|---|---|
| `ci-tests-unit.yaml` | `should-run` | Required check (`test`). Fixes
the original stall. |
| `ci-tests-e2e.yaml` | `should-run` | Required check (`e2e-status`).
Replaces inline filter. |
| `ci-perf-report.yaml` | `should-run` | Removes `paths-ignore`. |
| `ci-website-build.yaml` | `app-website-changes \|\| packages-changes`
| Refactor — not a required check, but moves to job-level gating. Filter
scope broadens from `packages/{design-system}` to all `packages/**`
(strictly safer). |
| `ci-website-e2e.yaml` | `app-website-changes \|\| packages-changes` |
Same restructure; `post-starting-comment` also gated to avoid spurious
"tests are running" when E2E is skipped. |
| `ci-dist-telemetry-scan.yaml` | `should-run` | New gate; was
previously running on every PR including docs-only. |
| `ci-oss-assets-validation.yaml` | `should-run` | Same. |
| `ci-size-data.yaml` | `should-run` | Preserves existing repository
guard on the new `changes` job. |
| `ci-tests-storybook.yaml` | `storybook-changes \|\|
app-frontend-changes \|\| packages-changes` | Gates 4 of 6 jobs.
`deploy-production` (push to main) left ungated;
`update-comment-with-chromatic` cascades naturally. |

## Branch protection (verified)

Required status checks on `main` and `core/**`/`cloud/**`: `test`,
`lint-and-format`, `e2e-status`. Only `test` and `e2e-status` use the
composite — `lint-and-format` correctly stays unfiltered (must run on
docs/apps too). The other 6 migrations are refactor wins (less wasted CI
on docs/apps-only PRs), not stall fixes.

## Changes

- **What**: New `.github/actions/changes-filter` composite + 8 workflow
migrations to consume it.
- **Breaking**: None.
- **Dependencies**: New pin on `dorny/paths-filter@de90cc6` — already
covered by `ci-validate-action-pins`.

## Review Focus

- The `should-run` filter excludes `.storybook/**` (granular
`storybook-changes` covers it instead). Storybook's gate combines all
three: `storybook-changes || app-frontend-changes || packages-changes`.
- Two `dorny/paths-filter` steps inside the composite —
`predicate-quantifier=every` is required for the negated globs in
`should-run` but breaks the multi-pattern OR filters.
- The website filter scope intentionally broadens from
`packages/{design-system,tailwind-utils}/**` to all `packages/**` for
consistency and safety.

Fixes #11776

┆Issue is synchronized with this [Notion
page](https://app.notion.com/p/PR-11785-ci-extract-changes-filter-composite-action-fix-docs-only-PR-stall-3526d73d36508172a1d7fe8c30fa6453)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Amp <amp@ampcode.com>

.github/workflows/ci-website-e2e.yaml

@@ -3,25 +3,29 @@ name: 'CI: Website E2E'
 on:
   push:
     branches: [main]
-    paths:
-      - 'apps/website/**'
-      - 'packages/design-system/**'
-      - 'packages/tailwind-utils/**'
-      - 'pnpm-lock.yaml'
   pull_request:
     branches-ignore: [wip/*, draft/*, temp/*]
-    paths:
-      - 'apps/website/**'
-      - 'packages/design-system/**'
-      - 'packages/tailwind-utils/**'
-      - 'pnpm-lock.yaml'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.repository }}-${{ github.head_ref || github.ref }}
   cancel-in-progress: true
 
 jobs:
+  changes:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    outputs:
+      app-website-changes: ${{ steps.changes.outputs.app-website-changes }}
+      packages-changes: ${{ steps.changes.outputs.packages-changes }}
+    steps:
+      - uses: actions/checkout@v6
+      - id: changes
+        uses: ./.github/actions/changes-filter
+
   website-e2e:
+    needs: changes
+    if: ${{ needs.changes.outputs.app-website-changes == 'true' || needs.changes.outputs.packages-changes == 'true' }}
     runs-on: ubuntu-latest
     container:
       image: mcr.microsoft.com/playwright:v1.58.1-noble
@@ -163,7 +167,11 @@ jobs:
   post-starting-comment:
     # Safe to comment from pull_request trigger: fork PRs are excluded by the guard below.
     # This avoids a ci-*/pr-* workflow_run split for a comment that must appear immediately.
-    if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork == false
+    needs: changes
+    if: |
+      github.event_name == 'pull_request'
+      && github.event.pull_request.head.repo.fork == false
+      && (needs.changes.outputs.app-website-changes == 'true' || needs.changes.outputs.packages-changes == 'true')
     runs-on: ubuntu-latest
     permissions:
       pull-requests: write