ci: run checks in weekly lockfile update workflow

[maxisbey]

Problem

PRs created by the weekly lockfile update workflow use GITHUB_TOKEN via peter-evans/create-pull-request. GitHub intentionally does not trigger on: pull_request workflows for PRs created this way (to prevent recursive workflow loops), so the CI workflow—and its all-green job—never runs, blocking merge.

Solution

Add workflow_dispatch to the CI workflow trigger, then dispatch it from the lockfile update workflow after creating the PR. GitHub explicitly exempts workflow_dispatch from the GITHUB_TOKEN event suppression, so CI runs on the PR branch HEAD commit and satisfies the required status check naturally.

Changes

• main.yml: Add workflow_dispatch trigger (no inputs needed—checkout defaults to the dispatched ref).
• weekly-lockfile-update.yml: After creating the PR, run gh workflow run main.yml --ref weekly-lockfile-update to trigger CI on the PR branch. Remove the inline checks and all-green jobs (no longer needed).
• shared.yml: Revert the ref input added previously (no longer needed since CI runs through main.yml on the correct ref).

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