refactor(scripts/github): split helpers into responsibility subfolders

Group the shell helpers under scripts/github/ into five subfolders
that match how the workflow files consume them:

  runner/   host-runner hygiene (disk, swap, Docker daemon, diagnostics)
  cancel/   run cancellation on PR-close and branch-delete events
  resolve/  derivation of workflow inputs and outputs from repo state
  update/   scheduled Update: Versions pipeline
  release/  release-time gates

Drop the now-redundant subfolder prefix from each filename, e.g.
dump_runner_state.sh becomes dump_state.sh and cancel_pull_request_runs.sh
becomes pull_request_runs.sh. Each subfolder carries a README that
describes its scope per documentation.md rules; the top-level README
points at the subfolders without inventorying files.

Propagate the new paths through ten workflow files, three docs
(workflow.md, pipeline.md, secrets.md), and two tests. Fix a real
runtime bug in enlarge_swap.sh, which still referenced the
pre-rename dump_runner_state.sh path. Extend the inline-block-size
lint hint to describe the new subfolder convention.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/github/update/install_python.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+python3 -m pip install --upgrade pip
+python3 -m pip install PyYAML