ci: regenerate SDK directly on merged spec changes

Spec updates land on main automatically, but the only generation
trigger is the nightly cron in PR mode, whose rolling PRs require a
manual merge (#205 sat open Apr 24 - Jun 11). Mirror typescript-sdk's
spec-change workflow: when a PR touching .speakeasy/in.openapi.yaml
merges to main, run Speakeasy in direct mode so the regenerated SDK
lands on main.

Author: robert-j-y

.github/workflows/sdk_generation_for_spec_change.yaml

@@ -0,0 +1,36 @@
+name: Generate (spec change merged)
+permissions:
+  checks: write
+  contents: write
+  pull-requests: write
+  statuses: write
+  id-token: write
+"on":
+  workflow_dispatch:
+    inputs:
+      force:
+        description: Force generation of SDKs
+        type: boolean
+        default: false
+      set_version:
+        description: optionally set a specific SDK version
+        type: string
+  pull_request:
+    types: [closed]
+    branches:
+      - main
+    paths:
+      - .speakeasy/in.openapi.yaml
+
+jobs:
+  generate:
+    if: github.event.pull_request.merged == true || github.event_name == 'workflow_dispatch'
+    uses: speakeasy-api/sdk-generation-action/.github/workflows/workflow-executor.yaml@v15
+    with:
+      force: ${{ github.event.inputs.force }}
+      mode: direct
+      set_version: ${{ github.event.inputs.set_version }}
+    secrets:
+      github_access_token: ${{ secrets.GITHUB_TOKEN }}
+      pypi_token: ${{ secrets.PYPI_TOKEN }}
+      speakeasy_api_key: ${{ secrets.SPEAKEASY_API_KEY }}