Adds a per-job/step Gantt chart (rendered as a mermaid diagram in the run
summary) to the 15 substantive CI workflows -- the 13 setup-backend
consumers plus superset-frontend.yml and docker.yml, the other two
heaviest CI paths. Skips trivial bot/label/notification workflows that run
in seconds and have nothing worth visualizing.
For single-job (or single-heavy-job-in-a-linear-chain) workflows, the step
is registered first, before checkout, so its post-processing hook -- which
is what actually renders the timeline -- captures the full job including
other steps' own cleanup. For workflows with multiple independent parallel
jobs, added a dedicated `actions-timeline` terminal job (`needs: [...]`,
`if: always()`) instead of duplicating the step into each parallel job:
the action fetches every job of the whole run from the GitHub API
regardless of which job it executes in, so one copy that runs after
every sibling job completes produces one authoritative timeline, while N
copies dropped into N parallel jobs would each race to render an
incomplete gantt before their siblings finish.
`expand-composite-actions: true` is set everywhere so setup-backend's
internal steps (Python setup, uv install, apt package caching, dependency
install) show up as their own bars rather than one opaque blob -- directly
useful given the last two PRs' worth of composite-action changes.
`actions: read` is added wherever needed to read job/step timing from the
Actions API, either to the workflow's top-level `permissions:` (when the
job in question has no job-level override) or directly into the relevant
job's own `permissions:` block (when one already exists, since a
job-level block replaces rather than merges with the workflow-level one).
