ci: run shared workflows on the CodeBuild runner

[wangyb-A]

Summary

Goal: run the shared-workflow jobs this repository calls (AI PR review, Slack notify, issue triage, stale-issue closer, OpenTelemetry conformance) on the CodeBuild-hosted runner in the Python testing account instead of the shared ubuntu-latest pool.

This completes the runner migration started in #747, which deliberately left these thin shells alone because their runs-on lives in the reusable workflows they call. Those now accept a runner input:

• aws/aws-durable-execution-ci — runs-on input on every workflow_call workflow (feat: add runs-on input to the shareable workflows aws-durable-execution-ci#67, not yet merged; see "Draft" below).
• aws/aws-durable-execution-conformance-tests — runs_on input on the OpenTelemetry orchestrator (ci: add runs_on input to the OTel orchestrator workflows aws-durable-execution-conformance-tests#132, merged as 3542852f).

What changed

Shell	Pin	Runner
ai-pr-review.yml, issue-triage.yml, notify.yml	d6b017da → d901b2f1	codebuild-github-actions-runner-${{ github.run_id }}-${{ github.run_attempt }}
stale-issue-closer.yml	48b3b434 → d901b2f1	same
opentelemetry-conformance-tests.yml	a628f558 → 3542852f	same, via runs_on

Every shell passes the label unconditionally. All of them run from main's workflow definition (pull_request_target, issues, release, schedule) or are already gated to same-repository PRs (opentelemetry-conformance-tests), and the AI review checks out the pull request's base revision and reads the diff as data, so no fork-authored code executes on the runner.

The pin bumps carry the intervening upstream commits: 12 on aws-durable-execution-ci (the runs-on input, the model-user scripts no longer assuming a runner account, the model environment passed as an explicit env -i allowlist, one stale-issue-closer fix, dependabot bumps) and 8 on aws-durable-execution-conformance-tests.

Draft

The CI-repo pin points at the head of aws/aws-durable-execution-ci#67's branch. When #67 merges (squash), one follow-up commit replaces it with the merge SHA; nothing else changes. Do not merge while the pin is a branch commit.

Verification

• Every with: key each shell passes was checked against the callee's workflow_call inputs at the new pin; all resolve.
• opentelemetry-conformance-tests is pull_request-triggered and the orchestrator change is on main, so this PR's own OTel run exercises the CodeBuild path end to end.
• The other shells run from main's definition, so this PR cannot exercise them; the first event after merge is the live test. The reusable Codex review was run end to end on the CodeBuild runner from the Update Model to use chained invoke over invoke #67 branch in aws-durable-execution-sdk-js run 37542509461, and the model-user scripts were exercised as root in run 37539805626.
• OTel job durations on recent PR runs are 3–8 minutes, under the project's 60-minute job limit.

no linked issue: follow-up to #747.