ci: remove OSCCA pull request triage workflow (#9361)

Stop automatically labeling OSCCA participants' pull requests with
z-ca-2026 and assigning them, and drop the matching zizmor ignore entry.

Assisted-by: Claude Code:claude-opus-5-5

.github/workflows/oscca-pr.yml

@@ -1,70 +0,0 @@
-name: Manage OSCCA pull requests
-
-on:
-  pull_request_target:
-    types: [opened]
-
-permissions: {}
-
-jobs:
-  label-and-assign:
-    name: Label and assign OSCCA pull request
-    runs-on: ubuntu-slim
-    timeout-minutes: 5
-    permissions:
-      pull-requests: write
-    steps:
-      - name: Label and assign pull request
-        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
-        with:
-          script: |
-            const osccaUsers = new Set(
-              [
-                "2jiyong",
-                "chestnut1717",
-                "devyubin",
-                "fregataa",
-                "hyoinandout",
-                "HyoJongPark",
-                "JaceJung-dev",
-                "jinmay",
-                "jiwahn",
-                "kangdora",
-                "kim-jaedeok",
-                "kyokuping",
-                "leehanjeong",
-                "lms0806",
-                "lsahn-gh",
-                "moreal",
-                "name-of-okja",
-                "rlaisqls",
-                "seungje0612",
-                "shAn-kor",
-                "sigmaith",
-                "teddygood",
-                "widehyo1",
-                "YangSiJun528",
-                "zzarbttoo",
-              ].map((login) => login.toLowerCase()),
-            );
-            const pullRequest = context.payload.pull_request;
-            const author = pullRequest.user.login;
-
-            if (!osccaUsers.has(author.toLowerCase())) {
-              core.info(`${author} is not an OSCCA participant; skipping.`);
-              return;
-            }
-
-            const issue = {
-              ...context.repo,
-              issue_number: pullRequest.number,
-            };
-
-            await github.rest.issues.addLabels({
-              ...issue,
-              labels: ["z-ca-2026"],
-            });
-            await github.rest.issues.addAssignees({
-              ...issue,
-              assignees: [author],
-            });

.github/zizmor.yml

@@ -1,9 +1,6 @@
 rules:
   dangerous-triggers:
     ignore:
-      # pull_request_target is needed to label and assign PRs from forks with issues: write.
-      # The workflow does not check out or execute pull request code.
-      - oscca-pr.yml:3
       # workflow_run is needed to post a PR comment from a fork's run, which is
       # handed a read-only token however the triggering workflow is configured.
       # The workflow does not check out or execute pull request code: it reads