VALID_CONFIG_KEYS: merge our additions (workflow.auto_advance,
workflow.node_repair, workflow.node_repair_budget, hooks.context_warnings)
with upstream's additions (workflow.text_mode, git.quick_branch_template).
ensureConfigFile(): keep our refactored version that delegates to
buildNewProjectConfig({}) instead of upstream's duplicated logic.
buildNewProjectConfig(): add git.quick_branch_template: null and
workflow.text_mode: false to match upstream's new keys.
new-project.md: integrate upstream's Step 5.1 Sub-Repo Detection
after our commit block; drop upstream's duplicate Note (ours at
line 493 is more detailed).
fd2a80675a