ci(build-exe): drop pull_request label trigger to avoid skipped checks (#3049)

* ci(build-exe): drop pull_request label trigger to avoid skipped checks

* docs(build-exe): sync agent note and pin event set in workflow spec

* test(ci): type-safe event key assertion for build-exe workflow

* ci(build-exe): use present-tense trigger comment and drop label-run note

.github/workflows/build-exe-for-python-sdk.yml

@@ -4,9 +4,10 @@ name: Build single-exe
 # .agents/notes/implemented/architecture/2026-07-10-single-file-executable-sdk-runtime-distribution.md.
 # A full target run retains one SDK wheel and four runtime wheels; subset
 # dispatch retains the SDK wheel and selected runtime wheels. Bare executables
-# and source closures are test inputs. Run manually, label a PR `build-exe`
-# (remove and reapply to rerun), or call it from the Python release workflow.
-# Checkout uses the triggering ref, so dispatch needs no separate ref input.
+# and source closures are test inputs. Run manually or call it from the Python
+# release workflow. There is no `pull_request` trigger: a label trigger would
+# list gray skipped checks on every unrelated PR label event. Checkout uses the
+# triggering ref, so dispatch needs no separate ref input.
 on:
   workflow_call:
     inputs:
@@ -39,8 +40,6 @@ on:
         type: string
         required: false
         default: ''
-  pull_request:
-    types: [labeled]
 
 concurrency:
   # Keep the called workflow distinct from its caller's concurrency group;
@@ -62,7 +61,7 @@ jobs:
   # construct the matrix before the dependent jobs.
   plan:
     name: plan targets
-    if: inputs.ci || inputs.release || github.event_name == 'workflow_dispatch' || github.event.label.name == 'build-exe'
+    if: inputs.ci || inputs.release || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
     timeout-minutes: 5
     outputs:
@@ -89,7 +88,7 @@ jobs:
       - name: Compute matrix from targets input
         id: plan
         env:
-          # Label runs and blank dispatch inputs build all targets.
+          # Blank dispatch inputs build all targets.
           TARGETS: ${{ inputs.targets || 'node24-linux-x64,node24-linux-arm64,node24-macos-arm64,node24-win-x64' }}
         run: |
           set -euo pipefail